diff --git a/tensorflow/python/ops/math_ops.py b/tensorflow/python/ops/math_ops.py
index f6f20444124c63..0f7727ae686cc2 100644
--- a/tensorflow/python/ops/math_ops.py
+++ b/tensorflow/python/ops/math_ops.py
@@ -1736,7 +1736,10 @@ def matmul(a,
     the product of the corresponding matrices in `a` and `b, e.g. if all
     transpose or adjoint attributes are `False`:
 
-    output[..., :, :] = a[..., :, :] * b[..., :, :] ,
+    `output`[..., i, j] = sum_k (`a`[..., i, k] * `b`[..., k, j]),
+    for all indices i, j.
+
+    Note: This is matrix product, not element-wise product.
 
 
   Raises: