diff --git a/planet/clients/features.py b/planet/clients/features.py
index 4aa3483b..4635edd5 100644
--- a/planet/clients/features.py
+++ b/planet/clients/features.py
@@ -300,3 +300,49 @@ async def add_items(self,
                                            json=feature,
                                            params=params)
         return list(resp.json())
+
+    async def update_item(self, collection_id: str, feature_id: str, feature: Union[dict, GeoInterface]) -> Feature:
+        """
+        Update an existing Feature identified by `feature_id` and `collection_id`.
+        Returns a Feature.
+
+        Note the Features API only accepts Polygon and MultiPolygon.
+
+        collection_id: the collection to add the feature to
+        feature: a dict containing a geojson Feature or FeatureCollection, or an
+          instance of a class that implements __geo_interface__ (e.g. a Shapely or
+          GeoPandas geometry object)
+
+        Example:
+
+        ```
+        updated_feature = await features_client.update_feature(
+          collection_id="my-collection",
+          feature_id="my-feature"
+          feature=feature,
+        )
+        ```
+
+        note: if a geojson Geometry is supplied, it will be converted
+        to a Feature. However, we recommend doing this conversion yourself
+        so that you can set a title and description property.
+        """
+        url = f'{self._base_url}/collections/{collection_id}/items/{feature_id}'
+
+        if isinstance(feature, GeoInterface):
+            # we expect __geo_interface__ to return a Geometry (not a Feature), so
+            # we're using the name `feature` liberally. We'll convert to a feature
+            # at the next step.
+            feature = feature.__geo_interface__
+
+        # convert a geojson geometry into geojson feature
+        if feature.get("type", "").lower() == "featurecollection":
+            raise ClientError("FeatureCollection is not supported, must provide a single feature")
+        if feature.get("type", "").lower() != "feature":
+            feature = {"type": "Feature", "geometry": feature}
+
+        response = await self._session.request(method='PUT',
+                                           url=url,
+                                           json=feature)
+
+        return Feature(**response.json())
\ No newline at end of file
diff --git a/planet/sync/features.py b/planet/sync/features.py
index c4cbee69..7681a041 100644
--- a/planet/sync/features.py
+++ b/planet/sync/features.py
@@ -190,3 +190,32 @@ def add_items(self,
                                                    property_id)
 
         return self._client._call_sync(uploaded_features)
+
+    def update_item(self, collection_id: str, feature_id: str, feature: Union[dict, GeoInterface]) -> Feature:
+        """
+        Update an existing Feature identified by `feature_id` and `collection_id`.
+        Returns a Feature.
+
+        Note the Features API only accepts Polygon and MultiPolygon.
+
+        collection_id: the collection to add the feature to
+        feature: a dict containing a geojson Feature or FeatureCollection, or an
+          instance of a class that implements __geo_interface__ (e.g. a Shapely or
+          GeoPandas geometry object)
+
+        Example:
+
+        ```
+        updated_feature = await features_client.update_feature(
+          collection_id="my-collection",
+          feature_id="my-feature"
+          feature=feature,
+        )
+        ```
+
+        note: if a geojson Geometry is supplied, it will be converted
+        to a Feature. However, we recommend doing this conversion yourself
+        so that you can set a title and description property.
+        """
+        return self._client._call_sync(
+            self._client.update_item(collection_id, feature_id, feature))