diff --git a/trl/trainer/grpo_config.py b/trl/trainer/grpo_config.py
index 9c4f4b3a68..af8ea9fd5a 100644
--- a/trl/trainer/grpo_config.py
+++ b/trl/trainer/grpo_config.py
@@ -37,6 +37,9 @@ class GRPOConfig(TrainingArguments):
         model_init_kwargs (`str`, `dict[str, Any]`, *optional*):
             Keyword arguments for [`~transformers.AutoModelForCausalLM.from_pretrained`], used when the `model`
             argument of the [`GRPOTrainer`] is provided as a string.
+        config_init_kwargs (`str`, `dict[str, Any]`, *optional*):
+            Keyword arguments for [`~transformers.AutoConfig.from_pretrained`], used when the `config`
+            argument of the [`GRPOTrainer`] is provided as a string.
         disable_dropout (`bool`, *optional*, defaults to `False`):
             Whether to disable dropout in the model. This is useful for training with a reference model, as it prevents
             the model from generating different logprobs for the same input.
@@ -242,7 +245,7 @@ class GRPOConfig(TrainingArguments):
             are logged.
     """
 
-    _VALID_DICT_FIELDS = TrainingArguments._VALID_DICT_FIELDS + ["model_init_kwargs"]
+    _VALID_DICT_FIELDS = TrainingArguments._VALID_DICT_FIELDS + ["model_init_kwargs", "config_init_kwargs"]
 
     # Parameters whose default values are overridden from TrainingArguments
     learning_rate: float = field(
@@ -279,6 +282,13 @@ class GRPOConfig(TrainingArguments):
             "argument of the `GRPOTrainer` is provided as a string."
         },
     )
+    config_init_kwargs: Optional[Union[dict, str]] = field(
+        default=None,
+        metadata={
+            "help": "Keyword arguments for `transformers.AutoConfig.from_pretrained`, used when the `config` "
+            "argument of the `GRPOTrainer` is provided as a string."
+        },
+    )
     disable_dropout: bool = field(
         default=False,
         metadata={
diff --git a/trl/trainer/grpo_trainer.py b/trl/trainer/grpo_trainer.py
index b3e1c716cd..02ddd2ef2f 100644
--- a/trl/trainer/grpo_trainer.py
+++ b/trl/trainer/grpo_trainer.py
@@ -225,6 +225,7 @@ def __init__(
         # Models
         # Trained model
         model_init_kwargs = args.model_init_kwargs or {}
+        config_init_kwargs = args.config_init_kwargs or {}
         if isinstance(model, str):
             model_id = model
             dtype = model_init_kwargs.get("dtype")
@@ -239,7 +240,7 @@ def __init__(
                     f"a `torch.dtype` (e.g., 'float32'), but got {dtype}."
                 )
             # Disable caching if gradient checkpointing is enabled (not supported)
-            config = AutoConfig.from_pretrained(model_id)
+            config = AutoConfig.from_pretrained(model_id, **config_init_kwargs)
             architecture = getattr(transformers, config.architectures[0])
             model = architecture.from_pretrained(model_id, **model_init_kwargs)
         else:
@@ -427,7 +428,7 @@ def __init__(
             self.ref_model = None
         else:
             # For deepspeed, fsdp or non-distributed models, create a reference model from scratch
-            config = AutoConfig.from_pretrained(model_id)
+            config = AutoConfig.from_pretrained(model_id, **config_init_kwargs)
             architecture = getattr(transformers, config.architectures[0])
             self.ref_model = architecture.from_pretrained(model_id, **model_init_kwargs)