diff --git a/bootstrap-app/src/cmr/bootstrap/api/resharding.clj b/bootstrap-app/src/cmr/bootstrap/api/resharding.clj
index df56fea062..7bdb60149b 100644
--- a/bootstrap-app/src/cmr/bootstrap/api/resharding.clj
+++ b/bootstrap-app/src/cmr/bootstrap/api/resharding.clj
@@ -5,7 +5,9 @@
    [cmr.bootstrap.api.messages :as msg]
    [cmr.bootstrap.api.util :as api-util]
    [cmr.bootstrap.services.bootstrap-service :as service]
-   [cmr.common.services.errors :as errors]))
+   [cmr.common.services.errors :as errors]
+   [cmr.elastic-utils.es-index-helper :as es-helper]
+   [cmr.elastic-utils.search.es-index :as es-index]))
 
 (defn- validate-num-shards
   "Validates that the number of shards is a positive integer."
@@ -27,11 +29,23 @@
   (when (string/blank? es-cluster-name)
     (errors/throw-service-error :bad-request "Empty elastic cluster name is not allowed.")))
 
+(defn- validate-index-exists
+  [context index es-cluster-name]
+  (let [conn (es-index/context->conn context es-cluster-name)]
+    (when-not (or (es-helper/exists? conn index)
+                  (es-helper/alias-exists? conn index))
+      (errors/throw-service-error
+       :not-found
+       (format "Index or alias [%s] does not exist in the Elasticsearch cluster [%s]"
+               index
+               es-cluster-name)))))
+
 (defn start
   "Kicks off resharding of an index."
   [context index params]
   (let [es-cluster-name (:elastic_name params)
         _ (validate-es-cluster-name-not-blank es-cluster-name)
+        _ (validate-index-exists context index es-cluster-name)
         num-shards-str (:num_shards params)
         _ (validate-num-shards num-shards-str)
         dispatcher (api-util/get-dispatcher context params :migrate-index)]
diff --git a/system-int-test/test/cmr/system_int_test/bootstrap/reshard_index_test.clj b/system-int-test/test/cmr/system_int_test/bootstrap/reshard_index_test.clj
index 45d035747f..42830da5af 100644
--- a/system-int-test/test/cmr/system_int_test/bootstrap/reshard_index_test.clj
+++ b/system-int-test/test/cmr/system_int_test/bootstrap/reshard_index_test.clj
@@ -62,7 +62,7 @@
               (bootstrap/start-reshard-index "1_small_collections" {:synchronous false :num-shards "abc" :elastic-name gran-elastic-name}))))
      (testing "index must exist"
        (is (= {:status 404
-               :errors ["Index [1_non-existing-index] does not exist."]}
+               :errors [(format "Index or alias [%s] does not exist in the Elasticsearch cluster [%s]" "1_non-existing-index" gran-elastic-name)]}
               (bootstrap/start-reshard-index "1_non-existing-index" {:synchronous false :num-shards 1 :elastic-name gran-elastic-name}))))
      (testing "attempting to reshard an index that is already being resharded fails"
        (is (= {:status 200