diff --git a/libs/partners/groq/langchain_groq/chat_models.py b/libs/partners/groq/langchain_groq/chat_models.py
index b221360a166..841f5c0a14b 100644
--- a/libs/partners/groq/langchain_groq/chat_models.py
+++ b/libs/partners/groq/langchain_groq/chat_models.py
@@ -75,6 +75,12 @@ from langchain_groq.data._profiles import _PROFILES
 from langchain_groq.version import __version__
 
 _MODEL_PROFILES = cast("ModelProfileRegistry", _PROFILES)
+_STRICT_STRUCTURED_OUTPUT_MODELS = frozenset(
+    {
+        "openai/gpt-oss-20b",
+        "openai/gpt-oss-120b",
+    }
+)
 
 
 def _get_default_model_profile(model_name: str) -> ModelProfile:
@@ -907,6 +913,7 @@ class ChatGroq(BaseChatModel):
             "function_calling", "json_mode", "json_schema"
         ] = "function_calling",
         include_raw: bool = False,
+        strict: bool | None = None,
         **kwargs: Any,
     ) -> Runnable[LanguageModelInput, dict | BaseModel]:
         r"""Model wrapper that returns outputs formatted to match the given schema.
@@ -979,6 +986,16 @@ class ChatGroq(BaseChatModel):
                 The final output is always a `dict` with keys `'raw'`, `'parsed'`, and
                 `'parsing_error'`.
 
+            strict:
+                Only used with `method="json_schema"`. When `True`, Groq's Structured
+                Output API uses constrained decoding to guarantee schema compliance.
+                This requires every object to set `additionalProperties: false` and
+                all properties to be listed in `required`. When `False`, schema
+                adherence is best-effort. If `None`, the argument is omitted.
+
+                Strict mode is only supported for `openai/gpt-oss-20b` and
+                `openai/gpt-oss-120b`. For other models, `strict=True` is ignored.
+
             kwargs:
                 Any additional parameters to pass to the `langchain.runnable.Runnable`
                 constructor.
@@ -1172,7 +1189,6 @@ class ChatGroq(BaseChatModel):
         ```
 
         """  # noqa: E501
-        _ = kwargs.pop("strict", None)
         is_pydantic_schema = _is_pydantic_class(schema)
         if method == "function_calling":
             if schema is None:
@@ -1210,14 +1226,25 @@ class ChatGroq(BaseChatModel):
                     "Received None."
                 )
                 raise ValueError(msg)
-            json_schema = convert_to_json_schema(schema)
+            if (
+                strict is True
+                and self.model_name not in _STRICT_STRUCTURED_OUTPUT_MODELS
+            ):
+                # Ignore unsupported strict=True to preserve backward compatibility.
+                strict = None
+            json_schema = convert_to_json_schema(schema, strict=strict)
             schema_name = json_schema.get("title", "")
-            response_format = {
+            response_format: dict[str, Any] = {
                 "type": "json_schema",
                 "json_schema": {"name": schema_name, "schema": json_schema},
             }
+            if strict is not None:
+                response_format["json_schema"]["strict"] = strict
+            ls_format_kwargs: dict[str, Any] = {"method": "json_schema"}
+            if strict is not None:
+                ls_format_kwargs["strict"] = strict
             ls_format_info = {
-                "kwargs": {"method": "json_schema"},
+                "kwargs": ls_format_kwargs,
                 "schema": json_schema,
             }
             llm = self.bind(
@@ -1247,8 +1274,9 @@ class ChatGroq(BaseChatModel):
             )
         else:
             msg = (
-                f"Unrecognized method argument. Expected one of 'function_calling' or "
-                f"'json_mode'. Received: '{method}'"
+                "Unrecognized method argument. Expected one of "
+                "'function_calling', 'json_mode', or 'json_schema'. "
+                f"Received: '{method}'"
             )
             raise ValueError(msg)
 
diff --git a/libs/partners/groq/tests/unit_tests/test_chat_models.py b/libs/partners/groq/tests/unit_tests/test_chat_models.py
index b4edc6bf0ac..1848f5f7ff3 100644
--- a/libs/partners/groq/tests/unit_tests/test_chat_models.py
+++ b/libs/partners/groq/tests/unit_tests/test_chat_models.py
@@ -16,6 +16,8 @@ from langchain_core.messages import (
     SystemMessage,
     ToolCall,
 )
+from langchain_core.runnables import RunnableBinding, RunnableSequence
+from pydantic import BaseModel
 
 from langchain_groq.chat_models import (
     ChatGroq,
@@ -256,6 +258,49 @@ def test_chat_groq_invalid_streaming_params() -> None:
         )
 
 
+def test_with_structured_output_json_schema_strict() -> None:
+    class Response(BaseModel):
+        """Response schema."""
+
+        foo: str
+
+    structured_model = ChatGroq(model="openai/gpt-oss-20b").with_structured_output(
+        Response, method="json_schema", strict=True
+    )
+
+    assert isinstance(structured_model, RunnableSequence)
+    first_step = structured_model.steps[0]
+    assert isinstance(first_step, RunnableBinding)
+    response_format = first_step.kwargs["response_format"]
+    assert response_format["type"] == "json_schema"
+    json_schema = response_format["json_schema"]
+    assert json_schema["strict"] is True
+    assert json_schema["name"] == "Response"
+    assert json_schema["schema"]["properties"]["foo"]["type"] == "string"
+    assert "foo" in json_schema["schema"]["required"]
+    assert json_schema["schema"]["additionalProperties"] is False
+
+
+def test_with_structured_output_json_schema_strict_ignored_on_unsupported_model() -> (
+    None
+):
+    class Response(BaseModel):
+        """Response schema."""
+
+        foo: str
+
+    structured_model = ChatGroq(model="llama-3.1-8b-instant").with_structured_output(
+        Response, method="json_schema", strict=True
+    )
+
+    assert isinstance(structured_model, RunnableSequence)
+    first_step = structured_model.steps[0]
+    assert isinstance(first_step, RunnableBinding)
+    response_format = first_step.kwargs["response_format"]
+    assert response_format["type"] == "json_schema"
+    assert "strict" not in response_format["json_schema"]
+
+
 def test_chat_groq_secret() -> None:
     """Test that secret is not printed."""
     secret = "secretKey"  # noqa: S105