diff --git a/tests/test_backend.py b/tests/test_backend.py
index 144f7ca76..c0e822a77 100755
--- a/tests/test_backend.py
+++ b/tests/test_backend.py
@@ -4698,6 +4698,17 @@ def func(x, y, z):
             return tf.identity(x_, name=_TFOUTPUT)
         self._run_test_case(func, [_OUTPUT], {_INPUT: x_val, _INPUT1: y_val, _INPUT2: z_val})
 
+    @check_opset_min_version(16, "ScatterND")
+    def test_scatternd_add(self):
+        x_val = np.array([10, 20, 30, 40], dtype=np.int32).reshape((4))
+        y_val = np.array([0, 2], dtype=np.int64).reshape((2, 1))
+        z_val = np.array([20, 30], dtype=np.int32).reshape((2))
+
+        def func(x, y, z):
+            x_ = tf.tensor_scatter_nd_add(x, y, z)
+            return tf.identity(x_, name=_TFOUTPUT)
+        self._run_test_case(func, [_OUTPUT], {_INPUT: x_val, _INPUT1: y_val, _INPUT2: z_val})
+
     @check_opset_min_version(11, "ScatterND")
     def test_scatternd_1d(self):
         x_val = np.array([4, 3, 1, 7], dtype=np.int32).reshape((4, 1))
diff --git a/tf2onnx/onnx_opset/tensor.py b/tf2onnx/onnx_opset/tensor.py
index 49564223e..9ad2b513e 100644
--- a/tf2onnx/onnx_opset/tensor.py
+++ b/tf2onnx/onnx_opset/tensor.py
@@ -655,6 +655,16 @@ def version_11(cls, ctx, node, **kwargs):
         ctx.replace_inputs(node, [node.input[2], node.input[0], node.input[1]])
 
 
+@tf_op("TensorScatterAdd", onnx_op="ScatterND")
+class TensorScatterAdd:
+    @classmethod
+    def version_16(cls, ctx, node, **kwargs):
+        # indicies input must be int64 in ONNX.
+        if ctx.get_dtype(node.input[1]) != TensorProto.INT64:
+            ctx.insert_new_node_on_input(node, "Cast", node.input[1], to=TensorProto.INT64)
+        node.set_attr("reduction", 'add')
+
+
 @tf_op("TensorScatterUpdate", onnx_op="ScatterND")
 class TensorScatterUpdate:
     @classmethod