diff --git a/lib/membership/member.ex b/lib/membership/member.ex
index 5816d19..286bb1a 100644
--- a/lib/membership/member.ex
+++ b/lib/membership/member.ex
@@ -329,6 +329,71 @@ defmodule Mv.Membership.Member do
         {:error, field: :email, message: "is not a valid email"}
       end
     end
+
+    # Validate required custom fields
+    validate fn changeset, _ ->
+      custom_field_values_arg = Ash.Changeset.get_argument(changeset, :custom_field_values)
+
+      # If argument is not provided (nil), check existing values from member data (update scenario)
+      # If argument is provided (empty list or list with values), use those values
+      provided_values =
+        if is_nil(custom_field_values_arg) do
+          # Update scenario: check existing custom field values from member
+          case Ash.load(changeset.data, :custom_field_values) do
+            {:ok, %{custom_field_values: existing_values}} ->
+              Enum.reduce(existing_values, %{}, fn cfv, acc ->
+                value = if is_map(cfv.value), do: Map.get(cfv.value, :value), else: nil
+                Map.put(acc, cfv.custom_field_id, value)
+              end)
+
+            _ ->
+              %{}
+          end
+        else
+          # Create or update scenario: use provided argument values
+          Enum.reduce(custom_field_values_arg, %{}, fn cfv, acc ->
+            custom_field_id = Map.get(cfv, "custom_field_id")
+            value_map = Map.get(cfv, "value", %{})
+
+            # Support both "value" and "_union_value" keys, without using || to preserve false values
+            actual_value =
+              cond do
+                Map.has_key?(value_map, "value") -> Map.get(value_map, "value")
+                Map.has_key?(value_map, "_union_value") -> Map.get(value_map, "_union_value")
+                true -> nil
+              end
+
+            Map.put(acc, custom_field_id, actual_value)
+          end)
+        end
+
+      # Load all required custom fields
+      case Mv.Membership.list_custom_fields() do
+        {:ok, all_custom_fields} ->
+          required_custom_fields = Enum.filter(all_custom_fields, & &1.required)
+
+          # Check each required custom field
+          missing_fields =
+            Enum.filter(required_custom_fields, fn cf ->
+              value = Map.get(provided_values, cf.id)
+              not value_present?(value, cf.value_type)
+            end)
+
+          if Enum.empty?(missing_fields) do
+            :ok
+          else
+            missing_names = Enum.map_join(missing_fields, ", ", & &1.name)
+
+            {:error,
+             field: :custom_field_values,
+             message: "Required custom fields missing: #{missing_names}"}
+          end
+
+        {:error, _} ->
+          # If we can't load custom fields, skip validation (shouldn't happen in normal operation)
+          :ok
+      end
+    end
   end
 
   attributes do
@@ -665,4 +730,18 @@ defmodule Mv.Membership.Member do
       query
     end
   end
+
+  # Helper function to check if a value is present for a given custom field type
+  # Boolean: false is valid, only nil is invalid
+  # String: nil or empty strings are invalid
+  # Integer: nil is invalid, 0 is valid
+  # Date: nil is invalid
+  # Email: nil is invalid
+  defp value_present?(nil, _type), do: false
+  defp value_present?(value, :boolean), do: not is_nil(value)
+  defp value_present?(value, :string), do: is_binary(value) and String.trim(value) != ""
+  defp value_present?(value, :integer), do: not is_nil(value)
+  defp value_present?(value, :date), do: not is_nil(value)
+  defp value_present?(value, :email), do: not is_nil(value)
+  defp value_present?(_value, _type), do: false
 end
diff --git a/lib/mv_web/live/member_live/form.ex b/lib/mv_web/live/member_live/form.ex
index 87148ad..3378504 100644
--- a/lib/mv_web/live/member_live/form.ex
+++ b/lib/mv_web/live/member_live/form.ex
@@ -144,6 +144,7 @@ defmodule MvWeb.MemberLive.Form do
                               field={value_form[:value]}
                               label={cf.name}
                               type={custom_field_input_type(cf.value_type)}
+                              required={cf.required}
                             />
                           </.inputs_for>
                           <input
diff --git a/test/membership/member_required_custom_fields_test.exs b/test/membership/member_required_custom_fields_test.exs
new file mode 100644
index 0000000..747cebd
--- /dev/null
+++ b/test/membership/member_required_custom_fields_test.exs
@@ -0,0 +1,525 @@
+defmodule Mv.Membership.MemberRequiredCustomFieldsTest do
+  @moduledoc """
+  Tests for required custom fields validation.
+
+  Tests cover:
+  - Member creation without required custom field → error
+  - Member creation with empty required custom field (nil/empty string) → error
+  - Member creation with valid required custom field → success
+  - Member update: removing a required custom field value → error
+  - Boolean required custom field: false is valid, nil is invalid
+  """
+  use Mv.DataCase, async: true
+
+  alias Mv.Membership
+
+  setup do
+    # Create required custom fields for different types
+    {:ok, required_string_field} =
+      Membership.CustomField
+      |> Ash.Changeset.for_create(:create, %{
+        name: "required_string",
+        value_type: :string,
+        required: true
+      })
+      |> Ash.create()
+
+    {:ok, required_integer_field} =
+      Membership.CustomField
+      |> Ash.Changeset.for_create(:create, %{
+        name: "required_integer",
+        value_type: :integer,
+        required: true
+      })
+      |> Ash.create()
+
+    {:ok, required_boolean_field} =
+      Membership.CustomField
+      |> Ash.Changeset.for_create(:create, %{
+        name: "required_boolean",
+        value_type: :boolean,
+        required: true
+      })
+      |> Ash.create()
+
+    {:ok, required_date_field} =
+      Membership.CustomField
+      |> Ash.Changeset.for_create(:create, %{
+        name: "required_date",
+        value_type: :date,
+        required: true
+      })
+      |> Ash.create()
+
+    {:ok, optional_field} =
+      Membership.CustomField
+      |> Ash.Changeset.for_create(:create, %{
+        name: "optional_string",
+        value_type: :string,
+        required: false
+      })
+      |> Ash.create()
+
+    %{
+      required_string_field: required_string_field,
+      required_integer_field: required_integer_field,
+      required_boolean_field: required_boolean_field,
+      required_date_field: required_date_field,
+      optional_field: optional_field
+    }
+  end
+
+  # Helper function to create all required custom fields with valid default values
+  defp all_required_custom_fields_with_defaults(%{
+         required_string_field: string_field,
+         required_integer_field: integer_field,
+         required_boolean_field: boolean_field,
+         required_date_field: date_field
+       }) do
+    [
+      %{
+        "custom_field_id" => string_field.id,
+        "value" => %{"_union_type" => "string", "_union_value" => "default"}
+      },
+      %{
+        "custom_field_id" => integer_field.id,
+        "value" => %{"_union_type" => "integer", "_union_value" => 0}
+      },
+      %{
+        "custom_field_id" => boolean_field.id,
+        "value" => %{"_union_type" => "boolean", "_union_value" => false}
+      },
+      %{
+        "custom_field_id" => date_field.id,
+        "value" => %{"_union_type" => "date", "_union_value" => ~D[2020-01-01]}
+      }
+    ]
+  end
+
+  describe "create_member with required custom fields" do
+    @valid_attrs %{
+      first_name: "John",
+      last_name: "Doe",
+      email: "john@example.com"
+    }
+
+    test "fails when required custom field is missing", %{required_string_field: field} do
+      attrs = Map.put(@valid_attrs, :custom_field_values, [])
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "fails when required string custom field has nil value",
+         %{
+           required_string_field: field
+         } = context do
+      # Start with all required fields having valid values
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "string", "_union_value" => nil}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "fails when required string custom field has empty string value",
+         %{
+           required_string_field: field
+         } = context do
+      # Start with all required fields having valid values
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "string", "_union_value" => ""}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "fails when required string custom field has whitespace-only value",
+         %{
+           required_string_field: field
+         } = context do
+      # Start with all required fields having valid values
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "string", "_union_value" => "   "}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "succeeds when required string custom field has valid value",
+         %{
+           required_string_field: field
+         } = context do
+      # Start with all required fields having valid values, then update the string field
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "string", "_union_value" => "test value"}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+
+    test "fails when required integer custom field has nil value",
+         %{
+           required_integer_field: field
+         } = context do
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "integer", "_union_value" => nil}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "succeeds when required integer custom field has zero value",
+         %{
+           required_integer_field: _field
+         } = context do
+      custom_field_values = all_required_custom_fields_with_defaults(context)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+
+    test "succeeds when required integer custom field has positive value",
+         %{
+           required_integer_field: field
+         } = context do
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "integer", "_union_value" => 42}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+
+    test "fails when required boolean custom field has nil value",
+         %{
+           required_boolean_field: field
+         } = context do
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "boolean", "_union_value" => nil}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "succeeds when required boolean custom field has false value",
+         %{
+           required_boolean_field: _field
+         } = context do
+      custom_field_values = all_required_custom_fields_with_defaults(context)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+
+    test "succeeds when required boolean custom field has true value",
+         %{
+           required_boolean_field: field
+         } = context do
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "boolean", "_union_value" => true}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+
+    test "fails when required date custom field has nil value",
+         %{
+           required_date_field: field
+         } = context do
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "date", "_union_value" => nil}}
+          else
+            cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "succeeds when required date custom field has valid date value",
+         %{
+           required_date_field: _field
+         } = context do
+      custom_field_values = all_required_custom_fields_with_defaults(context)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+
+    test "succeeds when multiple required custom fields are provided",
+         %{
+           required_string_field: string_field,
+           required_integer_field: integer_field,
+           required_boolean_field: boolean_field
+         } = context do
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          cond do
+            cfv["custom_field_id"] == string_field.id ->
+              %{cfv | "value" => %{"_union_type" => "string", "_union_value" => "test"}}
+
+            cfv["custom_field_id"] == integer_field.id ->
+              %{cfv | "value" => %{"_union_type" => "integer", "_union_value" => 42}}
+
+            cfv["custom_field_id"] == boolean_field.id ->
+              %{cfv | "value" => %{"_union_type" => "boolean", "_union_value" => true}}
+
+            true ->
+              cfv
+          end
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+
+    test "fails when one of multiple required custom fields is missing",
+         %{
+           required_string_field: string_field,
+           required_integer_field: integer_field
+         } = context do
+      # Provide only string field, missing integer, boolean, and date
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.filter(fn cfv ->
+          cfv["custom_field_id"] == string_field.id
+        end)
+        |> Enum.map(fn cfv ->
+          %{cfv | "value" => %{"_union_type" => "string", "_union_value" => "test"}}
+        end)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ integer_field.name
+    end
+
+    test "succeeds when optional custom field is missing", %{} = context do
+      # Provide all required fields, but no optional field
+      custom_field_values = all_required_custom_fields_with_defaults(context)
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+
+    test "succeeds when optional custom field has nil value",
+         %{optional_field: field} = context do
+      # Provide all required fields plus optional field with nil
+      custom_field_values =
+        all_required_custom_fields_with_defaults(context) ++
+          [
+            %{
+              "custom_field_id" => field.id,
+              "value" => %{"_union_type" => "string", "_union_value" => nil}
+            }
+          ]
+
+      attrs = Map.put(@valid_attrs, :custom_field_values, custom_field_values)
+
+      assert {:ok, _member} = Membership.create_member(attrs)
+    end
+  end
+
+  describe "update_member with required custom fields" do
+    test "fails when removing a required custom field value",
+         %{
+           required_string_field: field
+         } = context do
+      # Create member with all required custom fields
+      custom_field_values = all_required_custom_fields_with_defaults(context)
+
+      {:ok, member} =
+        Membership.create_member(%{
+          first_name: "John",
+          last_name: "Doe",
+          email: "john@example.com",
+          custom_field_values: custom_field_values
+        })
+
+      # Try to update without the required custom field
+      assert {:error, %Ash.Error.Invalid{errors: errors}} =
+               Membership.update_member(member, %{custom_field_values: []})
+
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "fails when setting required custom field value to empty",
+         %{
+           required_string_field: field
+         } = context do
+      # Create member with all required custom fields
+      custom_field_values = all_required_custom_fields_with_defaults(context)
+
+      {:ok, member} =
+        Membership.create_member(%{
+          first_name: "John",
+          last_name: "Doe",
+          email: "john@example.com",
+          custom_field_values: custom_field_values
+        })
+
+      # Try to update with empty value for the string field
+      updated_custom_field_values =
+        all_required_custom_fields_with_defaults(context)
+        |> Enum.map(fn cfv ->
+          if cfv["custom_field_id"] == field.id do
+            %{cfv | "value" => %{"_union_type" => "string", "_union_value" => ""}}
+          else
+            cfv
+          end
+        end)
+
+      assert {:error, %Ash.Error.Invalid{errors: errors}} =
+               Membership.update_member(member, %{
+                 custom_field_values: updated_custom_field_values
+               })
+
+      assert error_message(errors, :custom_field_values) =~ "Required custom fields missing"
+      assert error_message(errors, :custom_field_values) =~ field.name
+    end
+
+    test "succeeds when updating required custom field to valid value",
+         %{
+           required_string_field: field
+         } = context do
+      # Create member with all required custom fields
+      custom_field_values = all_required_custom_fields_with_defaults(context)
+
+      {:ok, member} =
+        Membership.create_member(%{
+          first_name: "John",
+          last_name: "Doe",
+          email: "john@example.com",
+          custom_field_values: custom_field_values
+        })
+
+      # Load existing custom field values to get their IDs
+      {:ok, member_with_cfvs} = Ash.load(member, :custom_field_values)
+
+      # Update with new valid value for the string field, using existing IDs
+      updated_custom_field_values =
+        member_with_cfvs.custom_field_values
+        |> Enum.map(fn cfv ->
+          if cfv.custom_field_id == field.id do
+            %{
+              "id" => cfv.id,
+              "custom_field_id" => cfv.custom_field_id,
+              "value" => %{"_union_type" => "string", "_union_value" => "new value"}
+            }
+          else
+            # Keep other fields as they are
+            value_type = Atom.to_string(cfv.value.type)
+            actual_value = cfv.value.value
+
+            %{
+              "id" => cfv.id,
+              "custom_field_id" => cfv.custom_field_id,
+              "value" => %{"_union_type" => value_type, "_union_value" => actual_value}
+            }
+          end
+        end)
+
+      assert {:ok, _updated_member} =
+               Membership.update_member(member, %{
+                 custom_field_values: updated_custom_field_values
+               })
+    end
+  end
+
+  # Helper function for error evaluation
+  defp error_message(errors, field) do
+    errors
+    |> Enum.filter(fn err -> Map.get(err, :field) == field end)
+    |> Enum.map_join(" ", &Map.get(&1, :message, ""))
+  end
+end