diff --git a/vllm/v1/kv_offload/base.py b/vllm/v1/kv_offload/base.py
index dc9d95499c..3d403ea508 100644
--- a/vllm/v1/kv_offload/base.py
+++ b/vllm/v1/kv_offload/base.py
@@ -331,12 +331,20 @@ class OffloadingSpec(ABC):
         assert kv_transfer_config is not None
         self.extra_config = kv_transfer_config.kv_connector_extra_config
 
+        parallel_config = vllm_config.parallel_config
+        context_parallel_factor = (
+            parallel_config.decode_context_parallel_size
+            * parallel_config.prefill_context_parallel_size
+        )
+
         # block size used by vLLM for hashing request tokens for the sake
         # of enabling prefix caching
-        self.hash_block_size = vllm_config.cache_config.block_size
+        self.hash_block_size = (
+            vllm_config.cache_config.block_size * context_parallel_factor
+        )
         # gpu block size per group
         self.gpu_block_size: tuple[int, ...] = tuple(
-            kv_cache_group.kv_cache_spec.block_size
+            kv_cache_group.kv_cache_spec.block_size * context_parallel_factor
             for kv_cache_group in kv_cache_config.kv_cache_groups
         )