diff --git a/src/AnthropicClient/Json/ContentConverter.cs b/src/AnthropicClient/Json/ContentConverter.cs
index e0183d4..d7fbd14 100644
--- a/src/AnthropicClient/Json/ContentConverter.cs
+++ b/src/AnthropicClient/Json/ContentConverter.cs
@@ -16,6 +16,7 @@ class ContentConverter : JsonConverter<Content>
     {
       ContentType.Text => JsonSerializer.Deserialize<TextContent>(root.GetRawText(), options)!,
       ContentType.Image => JsonSerializer.Deserialize<ImageContent>(root.GetRawText(), options)!,
+      ContentType.Document => JsonSerializer.Deserialize<DocumentContent>(root.GetRawText(), options)!,
       ContentType.ToolUse => JsonSerializer.Deserialize<ToolUseContent>(root.GetRawText(), options)!,
       ContentType.ToolResult => JsonSerializer.Deserialize<ToolResultContent>(root.GetRawText(), options)!,
       _ => throw new JsonException($"Unknown content type: {type}")
diff --git a/src/AnthropicClient/Models/DocumentContent.cs b/src/AnthropicClient/Models/DocumentContent.cs
new file mode 100644
index 0000000..1389d84
--- /dev/null
+++ b/src/AnthropicClient/Models/DocumentContent.cs
@@ -0,0 +1,56 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents content from a document that is part of a message.
+/// </summary>
+public class DocumentContent : Content
+{
+  /// <summary>
+  /// Gets the source of the document.
+  /// </summary>
+  public DocumentSource Source { get; init; } = new();
+
+  [JsonConstructor]
+  internal DocumentContent()
+  {
+  }
+
+  private void Validate(string mediaType, string data)
+  {
+    ArgumentValidator.ThrowIfNull(mediaType, nameof(mediaType));
+    ArgumentValidator.ThrowIfNull(data, nameof(data));
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="DocumentContent"/> class.
+  /// </summary>
+  /// <param name="mediaType">The media type of the document.</param>
+  /// <param name="data">The data of the document.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the media type or data is null.</exception>
+  /// <returns>A new instance of the <see cref="DocumentContent"/> class.</returns>
+  public DocumentContent(string mediaType, string data) : base(ContentType.Document)
+  {
+    Validate(mediaType, data);
+
+    Source = new(mediaType, data);
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="DocumentContent"/> class.
+  /// </summary>
+  /// <param name="mediaType">The media type of the document.</param>
+  /// <param name="data">The data of the document.</param>
+  /// <param name="cacheControl">The cache control to be used for the content.</param>
+  /// <returns>A new instance of the <see cref="DocumentContent"/> class.</returns>
+  /// <exception cref="ArgumentNullException">Thrown when the media type, data, or cache control is null.</exception>
+  public DocumentContent(string mediaType, string data, CacheControl cacheControl) : base(ContentType.Document, cacheControl)
+  {
+    Validate(mediaType, data);
+
+    Source = new(mediaType, data);
+  }
+}
\ No newline at end of file
diff --git a/src/AnthropicClient/Models/DocumentSource.cs b/src/AnthropicClient/Models/DocumentSource.cs
new file mode 100644
index 0000000..e18f978
--- /dev/null
+++ b/src/AnthropicClient/Models/DocumentSource.cs
@@ -0,0 +1,49 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a document source.
+/// </summary>
+public class DocumentSource
+{
+  /// <summary>
+  /// Gets the media type of the document.
+  /// </summary>
+  [JsonPropertyName("media_type")]
+  public string MediaType { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the data of the document.
+  /// </summary>
+  public string Data { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the type of encoding of the document data.
+  /// </summary>
+  public string Type { get; init; } = "base64";
+
+  [JsonConstructor]
+  internal DocumentSource()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="DocumentSource"/> class.
+  /// </summary>
+  /// <param name="mediaType">The media type of the document.</param>
+  /// <param name="data">The data of the document.</param>
+  /// <exception cref="ArgumentException">Thrown when the media type is invalid.</exception>
+  /// <exception cref="ArgumentNullException">Thrown when the media type or data is null.</exception>
+  /// <returns>A new instance of the <see cref="DocumentSource"/> class.</returns>
+  public DocumentSource(string mediaType, string data)
+  {
+    ArgumentValidator.ThrowIfNull(mediaType, nameof(mediaType));
+    ArgumentValidator.ThrowIfNull(data, nameof(data));
+
+    MediaType = mediaType;
+    Data = data;
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/DocumentContentTests.cs b/tests/AnthropicClient.Tests/Unit/Models/DocumentContentTests.cs
new file mode 100644
index 0000000..cec42f1
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/DocumentContentTests.cs
@@ -0,0 +1,119 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class DocumentContentTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""source"": { 
+      ""media_type"": ""application/pdf"",
+      ""data"": ""data"",
+      ""type"": ""base64""
+    },
+    ""type"": ""document""
+  }";
+
+  private readonly string _testJsonWithCacheControl = @"{
+    ""source"": { 
+      ""media_type"": ""application/pdf"",
+      ""data"": ""data"",
+      ""type"": ""base64""
+    },
+    ""cache_control"": { ""type"": ""ephemeral"" },
+    ""type"": ""document""
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeSource()
+  {
+    var expectedMediaType = "application/pdf";
+    var expectedData = "data";
+
+    var result = new DocumentContent(expectedMediaType, expectedData);
+
+    result.Source.Should().BeEquivalentTo(new DocumentSource(expectedMediaType, expectedData));
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledAndMediaTypeIsNull_ItShouldThrowArgumentNullException()
+  {
+    var expectedData = "data";
+
+    var action = () => new DocumentContent(null!, expectedData);
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledAndDataIsNull_ItShouldThrowArgumentNullException()
+  {
+    var expectedMediaType = "application/pdf";
+
+    var action = () => new DocumentContent(expectedMediaType, null!);
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithCacheControl_ItShouldInitializeSourceAndCacheControl()
+  {
+    var expectedMediaType = "application/pdf";
+    var expectedData = "data";
+    var cacheControl = new EphemeralCacheControl();
+
+    var result = new DocumentContent(expectedMediaType, expectedData, cacheControl);
+    
+    result.Source.Should().BeEquivalentTo(new DocumentSource(expectedMediaType, expectedData));
+    result.CacheControl.Should().BeSameAs(cacheControl);
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithCacheControlAndMediaTypeIsNull_ItShouldThrowArgumentNullException()
+  {
+    var expectedData = "data";
+    var cacheControl = new EphemeralCacheControl();
+
+    var action = () => new DocumentContent(null!, expectedData, cacheControl);
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithCacheControlAndDataIsNull_ItShouldThrowArgumentNullException()
+  {
+    var expectedMediaType = "application/pdf";
+    var cacheControl = new EphemeralCacheControl();
+
+    var action = () => new DocumentContent(expectedMediaType, null!, cacheControl);
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var content = new DocumentContent("application/pdf", "data");
+
+    var actual = Serialize(content);
+
+    JsonAssert.Equal(_testJson, actual);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerializedWithCacheControl_ItShouldHaveExpectedShape()
+  {
+    var content = new DocumentContent("application/pdf", "data", new EphemeralCacheControl());
+
+    var actual = Serialize(content);
+
+    JsonAssert.Equal(_testJsonWithCacheControl, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedShape()
+  {
+    var expected = new DocumentContent("application/pdf", "data");
+
+    var actual = Deserialize<DocumentContent>(_testJson);
+
+    actual.Should().BeEquivalentTo(expected);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/DocumentSourceTests.cs b/tests/AnthropicClient.Tests/Unit/Models/DocumentSourceTests.cs
new file mode 100644
index 0000000..60e2ec3
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/DocumentSourceTests.cs
@@ -0,0 +1,49 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class DocumentSourceTests
+{
+  [Fact]
+  public void Constructor_WhenCalledWithValidArguments_ItShouldSetProperties()
+  {
+    var mediaType = "application/pdf";
+    var data = "base64data";
+
+    var source = new DocumentSource(mediaType, data);
+
+    source.MediaType.Should().Be(mediaType);
+    source.Data.Should().Be(data);
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithNullMediaType_ItShouldThrowArgumentNullException()
+  {
+    string? mediaType = null;
+    var data = "base64data";
+
+    var action = () => new DocumentSource(mediaType!, data);
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithNullData_ItShouldThrowArgumentNullException()
+  {
+    var mediaType = "application/pdf";
+    string? data = null;
+
+    var action = () => new DocumentSource(mediaType, data!);
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldHaveTypePropertySetToBase64()
+  {
+    var mediaType = "application/pdf";
+    var data = "base64data";
+
+    var source = new DocumentSource(mediaType, data);
+
+    source.Type.Should().Be("base64");
+  }
+}
\ No newline at end of file