diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7dbf16f40..5a45c89f4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Changed
 
 - Changed assets serialization to prevent mapping explosion while allowing asset inforamtion to be indexed. [#341](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/341)
+- Blocked the /collections/{collection_id}/bulk_items endpoint when environmental variable ENABLE_DATETIME_INDEX_FILTERING is set to true. [#438](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/438)
 
 ### Fixed
 
diff --git a/stac_fastapi/core/stac_fastapi/core/core.py b/stac_fastapi/core/stac_fastapi/core/core.py
index 8e7da91bc..82d03894c 100644
--- a/stac_fastapi/core/stac_fastapi/core/core.py
+++ b/stac_fastapi/core/stac_fastapi/core/core.py
@@ -965,6 +965,13 @@ def bulk_item_insert(
             A string indicating the number of items successfully added.
         """
         request = kwargs.get("request")
+
+        if os.getenv("ENABLE_DATETIME_INDEX_FILTERING"):
+            raise HTTPException(
+                status_code=400,
+                detail="The /collections/{collection_id}/bulk_items endpoint is invalid when ENABLE_DATETIME_INDEX_FILTERING is set to true. Try using the /collections/{collection_id}/items endpoint.",
+            )
+
         if request:
             base_url = str(request.base_url)
         else: