diff --git a/llama-index-integrations/llms/llama-index-llms-vertex/llama_index/llms/vertex/base.py b/llama-index-integrations/llms/llama-index-llms-vertex/llama_index/llms/vertex/base.py
index 02971bd1833e9f..e327f863e9987c 100644
--- a/llama-index-integrations/llms/llama-index-llms-vertex/llama_index/llms/vertex/base.py
+++ b/llama-index-integrations/llms/llama-index-llms-vertex/llama_index/llms/vertex/base.py
@@ -16,6 +16,7 @@
 from llama_index.core.llms.callbacks import llm_chat_callback, llm_completion_callback
 from llama_index.core.llms.llm import LLM
 from llama_index.core.types import BaseOutputParser, PydanticProgramMode
+from llama_index.llms.gemini.utils import merge_neighboring_same_role_messages
 from llama_index.llms.vertex.gemini_utils import create_gemini_client, is_gemini_model
 from llama_index.llms.vertex.utils import (
     CHAT_MODELS,
@@ -130,7 +131,9 @@ def metadata(self) -> LLMMetadata:
         return LLMMetadata(
             is_chat_model=self._is_chat_model,
             model_name=self.model,
-            system_role=MessageRole.USER,  # Vertex does not support the default: MessageRole.SYSTEM
+            system_role=(
+                MessageRole.USER if self._is_gemini else MessageRole.SYSTEM
+            ),  # Gemini does not support the default: MessageRole.SYSTEM
         )
 
     @property
@@ -152,8 +155,13 @@ def _get_all_kwargs(self, **kwargs: Any) -> Dict[str, Any]:
 
     @llm_chat_callback()
     def chat(self, messages: Sequence[ChatMessage], **kwargs: Any) -> ChatResponse:
-        question = _parse_message(messages[-1], self._is_gemini)
-        chat_history = _parse_chat_history(messages[:-1], self._is_gemini)
+        merged_messages = (
+            merge_neighboring_same_role_messages(messages)
+            if self._is_gemini
+            else messages
+        )
+        question = _parse_message(merged_messages[-1], self._is_gemini)
+        chat_history = _parse_chat_history(merged_messages[:-1], self._is_gemini)
         chat_params = {**chat_history}
 
         kwargs = kwargs if kwargs else {}
@@ -209,8 +217,13 @@ def complete(
     def stream_chat(
         self, messages: Sequence[ChatMessage], **kwargs: Any
     ) -> ChatResponseGen:
-        question = _parse_message(messages[-1], self._is_gemini)
-        chat_history = _parse_chat_history(messages[:-1], self._is_gemini)
+        merged_messages = (
+            merge_neighboring_same_role_messages(messages)
+            if self._is_gemini
+            else messages
+        )
+        question = _parse_message(merged_messages[-1], self._is_gemini)
+        chat_history = _parse_chat_history(merged_messages[:-1], self._is_gemini)
         chat_params = {**chat_history}
         kwargs = kwargs if kwargs else {}
         params = {**self._model_kwargs, **kwargs}