diff --git a/.changelog/12637.txt b/.changelog/12637.txt
new file mode 100644
index 00000000000..dc7f825d150
--- /dev/null
+++ b/.changelog/12637.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+vertexai: made `contents_delta_uri` a optional field in `google_vertex_ai_index`
+```
\ No newline at end of file
diff --git a/google/services/vertexai/resource_vertex_ai_index.go b/google/services/vertexai/resource_vertex_ai_index.go
index 674a1587ba3..9dc80b1c5b8 100644
--- a/google/services/vertexai/resource_vertex_ai_index.go
+++ b/google/services/vertexai/resource_vertex_ai_index.go
@@ -90,16 +90,6 @@ Please refer to the field 'effective_labels' for all of the labels present on th
 				MaxItems:    1,
 				Elem: &schema.Resource{
 					Schema: map[string]*schema.Schema{
-						"contents_delta_uri": {
-							Type:     schema.TypeString,
-							Required: true,
-							Description: `Allows inserting, updating  or deleting the contents of the Matching Engine Index.
-The string must be a valid Cloud Storage directory path. If this
-field is set when calling IndexService.UpdateIndex, then no other
-Index field can be also updated as part of the same call.
-The expected structure and format of the files this URI points to is
-described at https://cloud.google.com/vertex-ai/docs/matching-engine/using-matching-engine#input-data-format`,
-						},
 						"config": {
 							Type:        schema.TypeList,
 							Optional:    true,
@@ -199,6 +189,16 @@ The shard size must be specified when creating an index. The value must be one o
 								},
 							},
 						},
+						"contents_delta_uri": {
+							Type:     schema.TypeString,
+							Optional: true,
+							Description: `Allows inserting, updating  or deleting the contents of the Matching Engine Index.
+The string must be a valid Cloud Storage directory path. If this
+field is set when calling IndexService.UpdateIndex, then no other
+Index field can be also updated as part of the same call.
+The expected structure and format of the files this URI points to is
+described at https://cloud.google.com/vertex-ai/docs/matching-engine/using-matching-engine#input-data-format`,
+						},
 						"is_complete_overwrite": {
 							Type:     schema.TypeBool,
 							Optional: true,
diff --git a/website/docs/r/vertex_ai_index.html.markdown b/website/docs/r/vertex_ai_index.html.markdown
index cad4e41ed6c..cdf13d6bb0d 100644
--- a/website/docs/r/vertex_ai_index.html.markdown
+++ b/website/docs/r/vertex_ai_index.html.markdown
@@ -161,7 +161,7 @@ The following arguments are supported:
 <a name="nested_metadata"></a>The `metadata` block supports:
 
 * `contents_delta_uri` -
-  (Required)
+  (Optional)
   Allows inserting, updating  or deleting the contents of the Matching Engine Index.
   The string must be a valid Cloud Storage directory path. If this
   field is set when calling IndexService.UpdateIndex, then no other