diff --git a/lib/bamboo/postmark_adapter.ex b/lib/bamboo/postmark_adapter.ex
index 4088f6e..e56f3c9 100644
--- a/lib/bamboo/postmark_adapter.ex
+++ b/lib/bamboo/postmark_adapter.ex
@@ -71,6 +71,9 @@ defmodule Bamboo.PostmarkAdapter do
     Map.merge(config, %{api_key: get_key(config)})
   end
 
+  @doc false
+  def supports_attachments?, do: true
+
   defp get_key(config) do
     api_key =
       case Map.get(config, :api_key) do
@@ -102,6 +105,22 @@ defmodule Bamboo.PostmarkAdapter do
     |> email_params()
     |> maybe_put_template_params(email)
     |> maybe_put_tag_params(email)
+    |> maybe_put_attachments(email)
+  end
+
+  def maybe_put_attachments(params, %{attachments: []}) do
+    params
+  end
+
+  def maybe_put_attachments(params, %{attachments: attachments}) do
+    params
+    |> Map.put(:"Attachments", Enum.map(attachments, fn attachment ->
+      %{
+        Name: attachment.filename,
+        Content: attachment.data |> Base.encode64(),
+        ContentType: attachment.content_type
+      }
+    end))
   end
 
   defp maybe_put_template_params(params, %{private:
diff --git a/test/lib/bamboo/postmark_adapter_test.exs b/test/lib/bamboo/postmark_adapter_test.exs
index e02041d..22e6a7d 100644
--- a/test/lib/bamboo/postmark_adapter_test.exs
+++ b/test/lib/bamboo/postmark_adapter_test.exs
@@ -217,6 +217,25 @@ defmodule Bamboo.PostmarkAdapterTest do
     }}
   end
 
+  test "deliver/2 puts attachments" do
+    email =
+      new_email()
+      |> Email.put_attachment(Path.join(__DIR__, "../../support/attachment.txt"))
+
+    PostmarkAdapter.deliver(email, @config)
+
+    assert_receive {
+      :fake_postmark,
+      %{
+        params: %{
+          "Attachments" => [
+            %{"Content" => "VGVzdCBBdHRhY2htZW50", "ContentType" => "text/plain", "Name" => "attachment.txt"}
+          ]
+        }
+      }
+    }
+  end
+
   test "raises if the response is not a success" do
     email = new_email(from: "INVALID_EMAIL")
 
diff --git a/test/support/attachment.txt b/test/support/attachment.txt
new file mode 100644
index 0000000..9a99f35
--- /dev/null
+++ b/test/support/attachment.txt
@@ -0,0 +1 @@
+Test Attachment
\ No newline at end of file