diff --git a/lib/graphql/resolver.ex b/lib/graphql/resolver.ex
index 671694d..0df70df 100644
--- a/lib/graphql/resolver.ex
+++ b/lib/graphql/resolver.ex
@@ -314,9 +314,9 @@ defmodule AshGraphql.Graphql.Resolver do
         Enum.find(action_arguments, &(&1.name == key)) || Enum.find(attributes, &(&1.name == key))
 
       if argument do
-        %{type: type, name: name} = argument
+        %{type: type, name: name, constraints: constraints} = argument
 
-        case handle_argument(type, value, name) do
+        case handle_argument(type, constraints, value, name) do
           {:ok, value} ->
             {:cont, {:ok, Map.put(arguments, name, value)}}
 
@@ -329,15 +329,81 @@ defmodule AshGraphql.Graphql.Resolver do
     end)
   end
 
-  defp handle_argument(type, value, name) do
-    if union_type?(type) do
-      handle_union_type(value, name)
-    else
-      {:ok, value}
+  defp handle_argument({:array, type}, constraints, value, name) when is_list(value) do
+    value
+    |> Enum.reduce_while({:ok, []}, fn value, {:ok, acc} ->
+      case handle_argument(type, constraints[:items], value, name) do
+        {:ok, value} ->
+          {:cont, {:ok, [value | acc]}}
+
+        {:error, error} ->
+          {:halt, {:error, error}}
+      end
+    end)
+    |> case do
+      {:ok, value} -> {:ok, Enum.reverse(value)}
+      {:error, error} -> {:error, error}
     end
   end
 
-  defp handle_union_type(value, name) do
+  defp handle_argument(Ash.Type.Union, constraints, value, name) do
+    handle_union_type(value, constraints, name)
+  end
+
+  defp handle_argument(type, constraints, value, name) do
+    if Ash.Type.embedded_type?(type) and is_map(value) do
+      create_action =
+        if constraints[:create_action] do
+          Ash.Resource.Info.action(type, constraints[:create_action]) ||
+            Ash.Resource.Info.primary_action(type, :create)
+        else
+          Ash.Resource.Info.primary_action(type, :create)
+        end
+
+      update_action =
+        if constraints[:update_action] do
+          Ash.Resource.Info.action(type, constraints[:update_action]) ||
+            Ash.Resource.Info.primary_action(type, :update)
+        else
+          Ash.Resource.Info.primary_action(type, :update)
+        end
+
+      attributes = Ash.Resource.Info.public_attributes(type)
+
+      fields =
+        cond do
+          create_action && update_action ->
+            create_action.arguments ++ update_action.arguments ++ attributes
+
+          update_action ->
+            update_action.arguments ++ attributes
+
+          create_action ->
+            create_action.arguments ++ attributes
+
+          true ->
+            attributes
+        end
+
+      {:ok,
+       Map.new(value, fn {key, value} ->
+         field =
+           Enum.find(fields, fn field ->
+             field.name == key
+           end)
+
+         if field do
+           {key, handle_argument(field.type, field.constraints, value, "#{name}.#{key}")}
+         else
+           {key, value}
+         end
+       end)}
+    end
+
+    {:ok, value}
+  end
+
+  defp handle_union_type(value, constraints, name) do
     value
     |> Enum.reject(fn {_key, value} ->
       is_nil(value)
@@ -346,8 +412,14 @@ defmodule AshGraphql.Graphql.Resolver do
       [] ->
         {:ok, nil}
 
-      [{_key, value}] ->
-        {:ok, value}
+      [{key, value}] ->
+        config = constraints[:types][key]
+
+        if config[:tag] && is_map(value) do
+          {:ok, Map.put_new(value, config[:tag], config[:tag_value])}
+        else
+          {:ok, value}
+        end
 
       key_vals ->
         keys = Enum.map_join(key_vals, ", ", fn {key, _} -> to_string(key) end)
@@ -357,10 +429,6 @@ defmodule AshGraphql.Graphql.Resolver do
     end
   end
 
-  defp union_type?({:array, type}), do: union_type?(type)
-  defp union_type?(Ash.Type.Union), do: true
-  defp union_type?(_), do: false
-
   def validate_resolve_opts(resolution, pagination, opts, args) do
     with page_opts <-
            args
diff --git a/lib/resource/resource.ex b/lib/resource/resource.ex
index f8af633..98b30fb 100644
--- a/lib/resource/resource.ex
+++ b/lib/resource/resource.ex
@@ -3100,7 +3100,7 @@ defmodule AshGraphql.Resource do
         AshGraphql.Resource.Info.type(type)
       else
         if Ash.Type.embedded_type?(type) do
-          if input? do
+          if input? && type(type) do
             :"#{AshGraphql.Resource.Info.type(resource)}_#{attribute.name}_input"
           else
             case type(type) do
diff --git a/test/create_test.exs b/test/create_test.exs
index d249a40..0ce810c 100644
--- a/test/create_test.exs
+++ b/test/create_test.exs
@@ -146,6 +146,64 @@ defmodule AshGraphql.CreateTest do
            } = result
   end
 
+  test "an embedded union type can be written to" do
+    resp =
+      """
+      mutation SimpleCreatePost($input: SimpleCreatePostInput) {
+        simpleCreatePost(input: $input) {
+          result{
+            text1
+            embedUnion {
+              ... on PostEmbedUnionFoo {
+                value {
+                  foo
+                }
+              }
+              ... on PostEmbedUnionBar {
+                value {
+                  bar
+                }
+              }
+            }
+          }
+          errors{
+            message
+          }
+        }
+      }
+      """
+      |> Absinthe.run(AshGraphql.Test.Schema,
+        variables: %{
+          "input" => %{
+            "text1" => "foo",
+            "embedUnion" => %{
+              "foo" => %{
+                "foo" => "10"
+              }
+            }
+          }
+        }
+      )
+
+    assert {:ok, result} = resp
+
+    refute Map.has_key?(result, :errors)
+
+    assert %{
+             data: %{
+               "simpleCreatePost" => %{
+                 "result" => %{
+                   "embedUnion" => %{
+                     "value" => %{
+                       "foo" => "10"
+                     }
+                   }
+                 }
+               }
+             }
+           } = result
+  end
+
   test "a create can load a calculation without selecting the fields the calculation needs" do
     resp =
       """
diff --git a/test/support/embeds.ex b/test/support/embeds.ex
new file mode 100644
index 0000000..1cc1e76
--- /dev/null
+++ b/test/support/embeds.ex
@@ -0,0 +1,47 @@
+defmodule Foo do
+  @moduledoc false
+  use Ash.Resource,
+    data_layer: :embedded,
+    extensions: [
+      AshGraphql.Resource
+    ]
+
+  graphql do
+    type :foo_embed
+  end
+
+  attributes do
+    attribute :type, :atom do
+      constraints(one_of: [:foo])
+      writable?(false)
+    end
+
+    attribute :foo, :string do
+      allow_nil? false
+    end
+  end
+end
+
+defmodule Bar do
+  @moduledoc false
+  use Ash.Resource,
+    data_layer: :embedded,
+    extensions: [
+      AshGraphql.Resource
+    ]
+
+  graphql do
+    type :bar_embed
+  end
+
+  attributes do
+    attribute :type, :atom do
+      constraints(one_of: [:foo])
+      writable?(false)
+    end
+
+    attribute :bar, :string do
+      allow_nil? false
+    end
+  end
+end
diff --git a/test/support/resources/post.ex b/test/support/resources/post.ex
index 140b0fe..1237d70 100644
--- a/test/support/resources/post.ex
+++ b/test/support/resources/post.ex
@@ -249,6 +249,23 @@ defmodule AshGraphql.Test.Post do
       ]
     )
 
+    attribute(:embed_union, :union,
+      constraints: [
+        types: [
+          foo: [
+            type: Foo,
+            tag: :type,
+            tag_value: :foo
+          ],
+          bar: [
+            type: Bar,
+            tag: :type,
+            tag_value: :bar
+          ]
+        ]
+      ]
+    )
+
     create_timestamp(:created_at, private?: false)
   end