diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4e22034fe..c175fbee2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Deprecated
 ### Removed
 ### Fixed
+- Fix `SmartSerializer` throwing `JsonException` on JSON with unpaired UTF-16 surrogate escape sequences produced by search highlighting ([#403](https://github.com/opensearch-project/opensearch-php/pull/403))
 ### Security
 ### Updated APIs
 
diff --git a/src/OpenSearch/Serializers/SmartSerializer.php b/src/OpenSearch/Serializers/SmartSerializer.php
index 79f70d08d..cf0725583 100644
--- a/src/OpenSearch/Serializers/SmartSerializer.php
+++ b/src/OpenSearch/Serializers/SmartSerializer.php
@@ -76,6 +76,15 @@ private function decode(?string $data): array
         try {
             return json_decode($data, true, 512, JSON_THROW_ON_ERROR);
         } catch (\JsonException $e) {
+            if ($e->getCode() === JSON_ERROR_UTF16) {
+                $escaped = str_replace('\\', '\\\\', $data);
+                try {
+                    return json_decode($escaped, true, 512, JSON_THROW_ON_ERROR);
+                } catch (\JsonException $e) {
+                    throw new JsonException($e->getCode(), $escaped, $e);
+                }
+            }
+
             throw new JsonException($e->getCode(), $data, $e);
         }
     }
diff --git a/tests/Serializers/SmartSerializerTest.php b/tests/Serializers/SmartSerializerTest.php
index 0080c1aaa..f5f06caf7 100644
--- a/tests/Serializers/SmartSerializerTest.php
+++ b/tests/Serializers/SmartSerializerTest.php
@@ -55,6 +55,28 @@ public function testThrowJsonException(): void
         }
     }
 
+    public function testDeserializeWithUnpairedUtf16Surrogates(): void
+    {
+        $data = '{ "data": "ud83d\\ude4f" }';
+
+        $result = $this->serializer->deserialize($data, []);
+
+        $this->assertIsArray($result);
+        $this->assertArrayHasKey('data', $result);
+        $this->assertSame('ud83d\\ude4f', $result['data']);
+    }
+
+    public function testDeserializeWithHighlightedSurrogatePair(): void
+    {
+        $data = '{ "data": "<em>\\ud83c</em>\\udd11" }';
+
+        $result = $this->serializer->deserialize($data, []);
+
+        $this->assertIsArray($result);
+        $this->assertArrayHasKey('data', $result);
+        $this->assertSame('<em>\\ud83c</em>\\udd11', $result['data']);
+    }
+
     public function testDeserialize(): void
     {
         $data = '{ "foo" : "bar" }';