diff --git a/vllm/v1/attention/backends/flex_attention.py b/vllm/v1/attention/backends/flex_attention.py
index c16a77c093cfb..928252636d583 100644
--- a/vllm/v1/attention/backends/flex_attention.py
+++ b/vllm/v1/attention/backends/flex_attention.py
@@ -896,6 +896,8 @@ def get_kernel_options(
         return kernel_options
     else:
         preferred_block = 32 if query.dtype == torch.float32 else 64
+        block_lower_bound = 16
+
         block_m_candidate = ensure_divisible(preferred_block, block_m)
         block_n_candidate = ensure_divisible(preferred_block, block_n)
 
@@ -910,6 +912,9 @@ def get_kernel_options(
                     max(1, block_n_candidate // 2), block_n
                 )
 
+        block_m_candidate = max(block_m_candidate, block_lower_bound)
+        block_n_candidate = max(block_n_candidate, block_lower_bound)
+
         kernel_options["BLOCK_M"] = block_m_candidate
         kernel_options["BLOCK_N"] = block_n_candidate