diff --git a/src/mcp/types/__init__.py b/src/mcp/types/__init__.py
index 666defaa2..b44230393 100644
--- a/src/mcp/types/__init__.py
+++ b/src/mcp/types/__init__.py
@@ -70,6 +70,7 @@
     GetTaskRequestParams,
     GetTaskResult,
     Icon,
+    IconTheme,
     ImageContent,
     Implementation,
     IncludeContext,
@@ -275,6 +276,7 @@
     "BlobResourceContents",
     "EmbeddedResource",
     "Icon",
+    "IconTheme",
     "ImageContent",
     "ResourceContents",
     "ResourceLink",
diff --git a/src/mcp/types/_types.py b/src/mcp/types/_types.py
index 26dfde7a6..42036eed7 100644
--- a/src/mcp/types/_types.py
+++ b/src/mcp/types/_types.py
@@ -28,6 +28,8 @@
 ProgressToken = str | int
 Role = Literal["user", "assistant"]
 
+IconTheme = Literal["light", "dark"]
+
 TaskExecutionMode = Literal["forbidden", "optional", "required"]
 TASK_FORBIDDEN: Final[Literal["forbidden"]] = "forbidden"
 TASK_OPTIONAL: Final[Literal["optional"]] = "optional"
@@ -170,6 +172,10 @@ class Icon(MCPModel):
     sizes: list[str] | None = None
     """Optional list of strings specifying icon dimensions (e.g., ["48x48", "96x96"])."""
 
+    theme: IconTheme | None = None
+    """Optional theme specifier. 'light' indicates the icon is designed for a light
+    background, 'dark' indicates the icon is designed for a dark background."""
+
 
 class Implementation(BaseMetadata):
     """Describes the name and version of an MCP implementation."""