diff --git a/tim/cli.py b/tim/cli.py
index fe35ba8..379add5 100644
--- a/tim/cli.py
+++ b/tim/cli.py
@@ -26,7 +26,7 @@
         },
         {
             "name": "Bulk record processing commands",
-            "commands": ["bulk-update", "reindex-source"],
+            "commands": ["bulk-update", "bulk-update-embeddings", "reindex-source"],
         },
     ]
 }
@@ -325,6 +325,101 @@ def bulk_update(
     logger.info(f"Bulk update complete: {json.dumps(summary_results)}")
 
 
+# Bulk update existing records with embeddings commands
+
+
+@main.command()
+@click.option(
+    "-i",
+    "--index",
+    help="Name of the index where the bulk update to add embeddings is performed.",
+)
+@click.option(
+    "-s",
+    "--source",
+    type=click.Choice(VALID_SOURCES),
+    help=(
+        "Source whose primary-aliased index will receive the bulk updated "
+        "records with embeddings."
+    ),
+)
+@click.option("-d", "--run-date", help="Run date, formatted as YYYY-MM-DD.")
+@click.option("-rid", "--run-id", help="Run ID.")
+@click.argument("dataset_path", type=click.Path())
+@click.pass_context
+def bulk_update_embeddings(
+    ctx: click.Context,
+    index: str,
+    source: str,
+    run_date: str,
+    run_id: str,
+    dataset_path: str,
+) -> None:
+    """Bulk update existing records with vector embeddings for an index.
+
+    Must provide either the name of an existing index in the cluster or a valid source.
+    If source is provided, it will update existing records for the primary-aliased
+    index for the source. If the provided index doesn't exist in the cluster, the
+    method will log an error and abort.
+
+    The method will read vector embeddings from a TIMDEXDataset
+    located at dataset_path using the 'timdex-dataset-api' library. The dataset
+    is filtered by run date and run ID.
+    """
+    client = ctx.obj["CLIENT"]
+    index = helpers.validate_bulk_cli_options(index, source, client)
+
+    logger.info(
+        f"Bulk updating records with embeddings from dataset '{dataset_path}' "
+        f"into '{index}'"
+    )
+
+    update_results = {"updated": 0, "errors": 0, "total": 0}
+
+    td = TIMDEXDataset(location=dataset_path)
+
+    # TODO @ghukill: https://mitlibraries.atlassian.net/browse/USE-143 # noqa: FIX002
+    # Remove temporary code and replace with TDA
+    # method to read embeddings
+    # ==== START TEMPORARY CODE ====
+    # The code below reads transformed records from
+    # the TIMDEX dataset. To simulate embeddings,
+    # which are added to the record post-creation, a list
+    # of dicts containing only the 'timdex_record_id' and
+    # the new field (i.e., what would be the embedding fields)
+    # is created. For simulation purposes, the 'alternate_titles'
+    # field represents the new field as it is already added
+    # to the OpenSearch mapping in config/opensearch_mappings.json.
+    # When testing, the user is expected to pass in a source that
+    # does not set this field (e.g., libguides).
+    # Once TDA has been updated to read/write embeddings
+    # from/to the TIMDEX dataset, this code should be replaced
+    # with a simple call to read vector embeddings, which should
+    # return an iter of dicts representing the embeddings.
+    transformed_records = td.read_transformed_records_iter(
+        run_date=run_date,
+        run_id=run_id,
+        action="index",
+    )
+
+    records_to_update = iter(
+        [
+            {
+                "timdex_record_id": record["timdex_record_id"],
+                "alternate_titles": [{"kind": "Test", "value": "Test Alternate Title"}],
+            }
+            for record in transformed_records
+        ]
+    )
+    # ==== END TEMPORARY CODE ====
+    try:
+        update_results.update(tim_os.bulk_update(client, index, records_to_update))
+    except BulkIndexingError as exception:
+        logger.info(f"Bulk update with embeddings failed: {exception}")
+
+    logger.info(f"Bulk update with embeddings complete: {json.dumps(update_results)}")
+
+
 @main.command()
 @click.option(
     "-s",
@@ -340,7 +435,12 @@ def bulk_update(
     help="Alias to promote the index to in addition to the primary alias. May "
     "be repeated to promote the index to multiple aliases at once.",
 )
-@click.argument("dataset_path", type=click.Path())
+@click.argument(
+    "dataset_path",
+    type=click.Path(),
+    help="Location of TIMDEX parquet dataset from which transformed records are read."
+    "This value can be a local filepath or an S3 URI.",
+)
 @click.pass_context
 def reindex_source(
     ctx: click.Context,
@@ -395,3 +495,7 @@ def reindex_source(
 
     summary_results = {"index": index_results}
     logger.info(f"Reindex source complete: {json.dumps(summary_results)}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tim/errors.py b/tim/errors.py
index 2905c68..184ad68 100644
--- a/tim/errors.py
+++ b/tim/errors.py
@@ -19,6 +19,22 @@ def __init__(self, record: str, index: str, error: str) -> None:
         super().__init__(self.message)
 
 
+class BulkOperationError(Exception):
+    """Exception raised when an unexpected error is returned during a bulk operation."""
+
+    def __init__(self, action: str, record: str, index: str, error: str) -> None:
+        """Initialize exception with provided index name and error for message."""
+        if action == "index":
+            verb = "indexing"
+        elif action == "update":
+            verb = "updating"
+
+        self.message = (
+            f"Error {verb} record '{record}' into index '{index}'. Details: {error}"
+        )
+        super().__init__(self.message)
+
+
 class IndexExistsError(Exception):
     """Exception raised when attempting to create an index that is already present."""
 
diff --git a/tim/helpers.py b/tim/helpers.py
index 2c195a5..f3d1cc4 100644
--- a/tim/helpers.py
+++ b/tim/helpers.py
@@ -50,8 +50,13 @@ def generate_bulk_actions(
             "_index": index,
             "_id": record["timdex_record_id"],
         }
-        if action != "delete":
-            doc["_source"] = record
+
+        match action:
+            case "update":
+                doc["doc"] = record
+            case _ if action != "delete":
+                doc["_source"] = record
+
         yield doc
 
 
diff --git a/tim/opensearch.py b/tim/opensearch.py
index 5b29643..2bf4d0e 100644
--- a/tim/opensearch.py
+++ b/tim/opensearch.py
@@ -17,6 +17,7 @@
 from tim.errors import (
     AliasNotFoundError,
     BulkIndexingError,
+    BulkOperationError,
     IndexExistsError,
     IndexNotFoundError,
 )
@@ -370,6 +371,10 @@ def bulk_index(client: OpenSearch, index: str, records: Iterator[dict]) -> dict[
     If an error occurs during record indexing, it will be logged and bulk indexing will
     continue until all records have been processed.
 
+    NOTE: The update performed by the "index" action results in a full replacement of the
+    document in OpenSearch. If a partial record is provided, this will result in a new
+    document in OpenSearch containing only the fields provided in the partial record.
+
     Returns total sums of: records created, records updated, errors, and total records
     processed.
     """
@@ -413,3 +418,54 @@ def bulk_index(client: OpenSearch, index: str, records: Iterator[dict]) -> dict[
     )
     logger.debug(response)
     return result
+
+
+def bulk_update(
+    client: OpenSearch, index: str, records: Iterator[dict]
+) -> dict[str, int]:
+    """Updates existing documents in the index using the streaming bulk helper.
+
+    This method uses the OpenSearch "update" action, which updates existing documents
+    and returns an error if the document does not exist. The "update" action can accept
+    a full or partial record and will only update the corresponding fields in the
+    document.
+
+    Returns total sums of: records updated, errors, and total records
+    processed.
+    """
+    result = {"updated": 0, "errors": 0, "total": 0}
+    actions = helpers.generate_bulk_actions(index, records, "update")
+    responses = streaming_bulk(
+        client,
+        actions,
+        max_chunk_bytes=REQUEST_CONFIG["OPENSEARCH_BULK_MAX_CHUNK_BYTES"],
+        raise_on_error=False,
+    )
+    for response in responses:
+        if response[0] is False:
+            error = response[1]["update"]["error"]
+            record = response[1]["update"]["_id"]
+            if error["type"] == "mapper_parsing_exception":
+                logger.error(
+                    "Error updating record '%s'. Details: %s",
+                    record,
+                    json.dumps(error),
+                )
+                result["errors"] += 1
+            else:
+                raise BulkOperationError(
+                    "update", record, index, json.dumps(error)  # noqa: EM101
+                )
+        elif response[1]["update"].get("result") == "updated":
+            result["updated"] += 1
+        else:
+            logger.error(
+                "Something unexpected happened during update. Bulk update response: %s",
+                json.dumps(response),
+            )
+            result["errors"] += 1
+        result["total"] += 1
+        if result["total"] % int(os.getenv("STATUS_UPDATE_INTERVAL", "1000")) == 0:
+            logger.info("Status update: %s records updated so far!", result["total"])
+    logger.debug(response)
+    return result