diff --git a/python/tvm/relax/frontend/onnx/onnx_frontend.py b/python/tvm/relax/frontend/onnx/onnx_frontend.py
index 32b2c508f009..f6bde18b8db5 100644
--- a/python/tvm/relax/frontend/onnx/onnx_frontend.py
+++ b/python/tvm/relax/frontend/onnx/onnx_frontend.py
@@ -564,15 +564,14 @@ def _impl_v18(cls, bb, inputs, attr, params):
         return cls.base_impl(bb, inputs, attr, params)
 
 
-class BitwiseNot(BitwiseBase):
+class BitwiseNot(OnnxOpConverter):
     """Converts an onnx BitwiseNot node into an equivalent Relax expression."""
 
-    numpy_op = _np.bitwise_not
-    relax_op = relax.op.bitwise_not
-
     @classmethod
     def _impl_v18(cls, bb, inputs, attr, params):
-        return cls.base_impl(bb, inputs, attr, params)
+        if isinstance(inputs[0], relax.Constant):
+            return relax.const(_np.bitwise_not(inputs[0].data.numpy()), inputs[0].struct_info.dtype)
+        return relax.op.bitwise_not(inputs[0])
 
 
 class BitShift(BitwiseBase):
@@ -3117,13 +3116,13 @@ def _get_convert_map():
         "BitwiseAnd": BitwiseAnd,
         "BitwiseOr": BitwiseOr,
         "BitwiseXor": BitwiseXor,
-        "BitwiseNot": BitwiseNot,
         "BitShift": BitShift,
         "And": And,
         "Or": Or,
         "Xor": Xor,
         "Not": Not,
         # Unary operators
+        "BitwiseNot": BitwiseNot,
         "Log": Log,
         "Exp": Exp,
         "Acos": Acos,
diff --git a/tests/python/relax/test_frontend_onnx.py b/tests/python/relax/test_frontend_onnx.py
index b7305d4810ed..6c3334f64d12 100644
--- a/tests/python/relax/test_frontend_onnx.py
+++ b/tests/python/relax/test_frontend_onnx.py
@@ -402,13 +402,11 @@ def test_binary_bool(op_name: str):
     verify_binary(op_name, [32, 32], [32, 32], [32, 32], dtype=TensorProto.BOOL)
 
 
-@pytest.mark.skip(reason="opset 18 is not supported in CI")
 @pytest.mark.parametrize("op_name", ["BitwiseAnd", "BitwiseOr", "BitwiseXor"])
 def test_bitwise(op_name: str):
     verify_binary(op_name, [32, 32], [32, 32], [32, 32], dtype=TensorProto.UINT64, opset=18)
 
 
-@pytest.mark.skip(reason="opset 18 is not supported in CI")
 def test_bitwise_not():
     verify_unary(
         "BitwiseNot",
@@ -945,7 +943,6 @@ def test_selu():
     verify_unary("Selu", [3, 32, 32], attrs={"alpha": 0.25, "gamma": 0.3})
 
 
-@pytest.mark.skip(reason="opset 18 is not supported in CI")
 def test_mish():
     verify_unary("Mish", [3, 32, 32], opset=18)