diff --git a/src/Resend/EmailMessageTemplate.cs b/src/Resend/EmailMessageTemplate.cs
index 2bddc6e..9a053fa 100644
--- a/src/Resend/EmailMessageTemplate.cs
+++ b/src/Resend/EmailMessageTemplate.cs
@@ -6,10 +6,10 @@ namespace Resend;
 public class EmailMessageTemplate
 {
     /// <summary>
-    /// Identifier of published template.
+    /// Identifier or alias of the published template.
     /// </summary>
     [JsonPropertyName( "id" )]
-    public Guid TemplateId { get; set; }
+    public string TemplateId { get; set; } = default!;
 
     /// <summary>
     /// Template variables.
diff --git a/tests/Resend.Tests/EmailMessageTemplateTests.cs b/tests/Resend.Tests/EmailMessageTemplateTests.cs
new file mode 100644
index 0000000..d7c7828
--- /dev/null
+++ b/tests/Resend.Tests/EmailMessageTemplateTests.cs
@@ -0,0 +1,37 @@
+using System.Text.Json;
+
+namespace Resend.Tests;
+
+/// <summary />
+public class EmailMessageTemplateTests
+{
+    /// <summary />
+    [Fact]
+    public void SerializesAliasId()
+    {
+        var message = new EmailMessage()
+        {
+            From = "from@example.com",
+            To = "to@example.com",
+            Template = new EmailMessageTemplate() { TemplateId = "welcome-email" },
+        };
+
+        var json = JsonSerializer.Serialize( message );
+
+        Assert.Contains( "\"id\":\"welcome-email\"", json );
+    }
+
+
+    /// <summary />
+    [Fact]
+    public void RoundtripsAliasId()
+    {
+        var template = new EmailMessageTemplate() { TemplateId = "welcome-email" };
+
+        var json = JsonSerializer.Serialize( template );
+        var actual = JsonSerializer.Deserialize<EmailMessageTemplate>( json );
+
+        Assert.NotNull( actual );
+        Assert.Equal( "welcome-email", actual.TemplateId );
+    }
+}