diff --git a/.gitignore b/.gitignore
index cff7bce..89e38d1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -160,5 +160,4 @@ cython_debug/
 #.idea/
 
 *.onnx
-*.textproto
 *.pb
diff --git a/src/model_explorer_onnx/main.py b/src/model_explorer_onnx/main.py
index bf232a3..d191b30 100644
--- a/src/model_explorer_onnx/main.py
+++ b/src/model_explorer_onnx/main.py
@@ -54,9 +54,14 @@ def can_display_tensor_json(
     return True
 
 
-def display_tensor_json(tensor: ir.TensorProtocol | None, settings: Settings) -> str:
+def display_tensor_json(
+    tensor: ir.TensorProtocol | np.ndarray, settings: Settings
+) -> str:
     try:
-        array = _tensor_to_numpy(tensor)
+        if isinstance(tensor, np.ndarray):
+            array = tensor
+        else:
+            array = _tensor_to_numpy(tensor)
         size_limit = settings.const_element_count_limit
         if size_limit < 0 or size_limit >= array.size:
             # Use separators=(',', ':') to remove spaces
@@ -215,12 +220,27 @@ def add_node_attrs(
         if isinstance(attr, ir.Attr):
             if attr.type == ir.AttributeType.TENSOR:
                 if can_display_tensor_json(attr.value, settings=settings):
+                    assert attr.value is not None
                     set_attr(
                         node,
                         "__value",
                         display_tensor_json(attr.value, settings=settings),
                     )
                 attr_value = display_tensor_repr(attr.value)
+            elif onnx_node.op_type == "Constant" and attr.name in {
+                "value_float",
+                "value_int",
+                "value_string",
+                "value_floats",
+                "value_ints",
+                "value_strings",
+            }:
+                set_attr(
+                    node,
+                    "__value",
+                    display_tensor_json(np.array(attr.value), settings=settings),
+                )
+                attr_value = str(attr.value)
             elif onnx_node.op_type == "Cast" and attr.name == "to":
                 attr_value = str(ir.DataType(attr.value))
             else:
@@ -417,6 +437,7 @@ def add_initializers(
             node = all_nodes[initializer_node_name]
             metadata = node.outputsMetadata[0]
             if can_display_tensor_json(initializer.const_value, settings=settings):
+                assert initializer.const_value is not None
                 set_attr(
                     node,
                     "__value",
@@ -440,6 +461,7 @@ def add_initializers(
         set_attr(metadata, "__tensor_tag", initializer.name or "")
         set_type_shape_metadata(metadata, initializer.const_value)
         if can_display_tensor_json(initializer.const_value, settings=settings):
+            assert initializer.const_value is not None
             set_attr(
                 node,
                 "__value",
diff --git a/testdata/constant_node_tests.textproto b/testdata/constant_node_tests.textproto
new file mode 100644
index 0000000..a048b86
--- /dev/null
+++ b/testdata/constant_node_tests.textproto
@@ -0,0 +1,107 @@
+ir_version: 8
+graph {
+  node {
+    output: "val_0"
+    name: "node_Constant_0"
+    op_type: "Constant"
+    attribute {
+      name: "value_int"
+      i: 42
+      type: INT
+    }
+  }
+  node {
+    input: "val_0"
+    output: "val_1"
+    name: "node_Identity_1"
+    op_type: "Identity"
+  }
+  node {
+    output: "val_2"
+    name: "node_Constant_2"
+    op_type: "Constant"
+    attribute {
+      name: "value_ints"
+      ints: 0
+      ints: 42
+      type: INTS
+    }
+  }
+  node {
+    input: "val_2"
+    output: "val_3"
+    name: "node_Identity_3"
+    op_type: "Identity"
+  }
+  node {
+    output: "val_4"
+    name: "node_Constant_4"
+    op_type: "Constant"
+    attribute {
+      name: "value_float"
+      f: 42.0
+      type: FLOAT
+    }
+  }
+  node {
+    input: "val_4"
+    output: "val_5"
+    name: "node_Identity_5"
+    op_type: "Identity"
+  }
+  node {
+    output: "val_6"
+    name: "node_Constant_6"
+    op_type: "Constant"
+    attribute {
+      name: "value_floats"
+      floats: 0.0
+      floats: 3.1415927
+      type: FLOATS
+    }
+  }
+  node {
+    input: "val_6"
+    output: "val_7"
+    name: "node_Identity_7"
+    op_type: "Identity"
+  }
+  node {
+    output: "val_8"
+    name: "node_Constant_8"
+    op_type: "Constant"
+    attribute {
+      name: "value_string"
+      s: "hello"
+      type: STRING
+    }
+  }
+  node {
+    input: "val_8"
+    output: "val_9"
+    name: "node_Identity_9"
+    op_type: "Identity"
+  }
+  node {
+    output: "val_10"
+    name: "node_Constant_10"
+    op_type: "Constant"
+    attribute {
+      name: "value_strings"
+      strings: "hello"
+      strings: "world"
+      type: STRINGS
+    }
+  }
+  node {
+    input: "val_10"
+    output: "val_11"
+    name: "node_Identity_11"
+    op_type: "Identity"
+  }
+  name: "constant_node_tests"
+}
+opset_import {
+  domain: ""
+  version: 20
+}
diff --git a/tools/test_generation/constant_node_tests.py b/tools/test_generation/constant_node_tests.py
new file mode 100644
index 0000000..3ec7535
--- /dev/null
+++ b/tools/test_generation/constant_node_tests.py
@@ -0,0 +1,58 @@
+import math
+import pathlib
+
+import onnx
+from onnxscript import ir
+
+
+def main():
+    graph = ir.Graph(
+        [],
+        [],
+        nodes=[
+            c1 := ir.Node(
+                "", "Constant", [], attributes=[ir.AttrInt64("value_int", 42)]
+            ),
+            ir.Node("", "Identity", c1.outputs),
+            c2 := ir.Node(
+                "", "Constant", [], attributes=[ir.AttrInt64s("value_ints", [0, 42])]
+            ),
+            ir.Node("", "Identity", c2.outputs),
+            c3 := ir.Node(
+                "", "Constant", [], attributes=[ir.AttrFloat32("value_float", 42.0)]
+            ),
+            ir.Node("", "Identity", c3.outputs),
+            c4 := ir.Node(
+                "",
+                "Constant",
+                [],
+                attributes=[ir.AttrFloat32s("value_floats", [0.0, math.pi])],
+            ),
+            ir.Node("", "Identity", c4.outputs),
+            c5 := ir.Node(
+                "", "Constant", [], attributes=[ir.AttrString("value_string", "hello")]
+            ),
+            ir.Node("", "Identity", c5.outputs),
+            c6 := ir.Node(
+                "",
+                "Constant",
+                [],
+                attributes=[ir.AttrStrings("value_strings", ["hello", "world"])],
+            ),
+            ir.Node("", "Identity", c6.outputs),
+        ],
+        opset_imports={"": 20},
+        name="constant_node_tests",
+    )
+    model = ir.Model(graph, ir_version=8)
+    model_proto = ir.serde.serialize_model(model)
+    onnx.save(
+        model_proto,
+        pathlib.Path(__file__).parent.parent.parent
+        / "testdata"
+        / "constant_node_tests.textproto",
+    )
+
+
+if __name__ == "__main__":
+    main()