diff --git a/comfy_extras/nodes_dataset.py b/comfy_extras/nodes_dataset.py
index 71e5ee368..81365717f 100644
--- a/comfy_extras/nodes_dataset.py
+++ b/comfy_extras/nodes_dataset.py
@@ -1077,7 +1077,10 @@ class NormalizeImagesNode(ImageProcessingNode):
 
     @classmethod
     def _process(cls, image, mean, std):
-        return (image - mean) / std
+        out = (image - mean) / std
+        if image.shape[-1] == 4:  # alpha stores transparency, not color
+            out[..., 3] = image[..., 3]
+        return out
 
 
 class AdjustBrightnessNode(ImageProcessingNode):
@@ -1099,7 +1102,10 @@ class AdjustBrightnessNode(ImageProcessingNode):
 
     @classmethod
     def _process(cls, image, factor):
-        return (image * factor).clamp(0.0, 1.0)
+        out = (image * factor).clamp(0.0, 1.0)
+        if image.shape[-1] == 4:  # alpha stores transparency, not color
+            out[..., 3] = image[..., 3]
+        return out
 
 
 class AdjustContrastNode(ImageProcessingNode):
@@ -1121,7 +1127,10 @@ class AdjustContrastNode(ImageProcessingNode):
 
     @classmethod
     def _process(cls, image, factor):
-        return ((image - 0.5) * factor + 0.5).clamp(0.0, 1.0)
+        out = ((image - 0.5) * factor + 0.5).clamp(0.0, 1.0)
+        if image.shape[-1] == 4:  # alpha stores transparency, not color
+            out[..., 3] = image[..., 3]
+        return out
 
 
 class ShuffleDatasetNode(ImageProcessingNode):
diff --git a/tests-unit/comfy_extras_test/dataset_color_nodes_alpha_test.py b/tests-unit/comfy_extras_test/dataset_color_nodes_alpha_test.py
new file mode 100644
index 000000000..70b63abd6
--- /dev/null
+++ b/tests-unit/comfy_extras_test/dataset_color_nodes_alpha_test.py
@@ -0,0 +1,78 @@
+import pytest
+import torch
+
+from comfy.cli_args import args as cli_args
+
+if not torch.cuda.is_available():
+    cli_args.cpu = True
+
+from comfy_extras.nodes_dataset import (  # noqa: E402
+    AdjustBrightnessNode,
+    AdjustContrastNode,
+    NormalizeImagesNode,
+)
+
+# (node, kwargs) for each colour adjustment that must leave alpha alone.
+CASES = [
+    (NormalizeImagesNode, {"mean": 0.5, "std": 0.5}),
+    (AdjustBrightnessNode, {"factor": 1.5}),
+    (AdjustContrastNode, {"factor": 1.5}),
+]
+IDS = [node.__name__ for node, _ in CASES]
+
+
+def image(channels, value=0.25, alpha=0.8, size=4):
+    # alpha 0.8 on purpose: 0.0, 0.5 and 1.0 are fixed points of one or more of
+    # these transforms, so they would hide the bug.
+    t = torch.full((1, size, size, channels), value)
+    if channels == 4:
+        t[..., 3] = alpha
+    return t
+
+
+@pytest.mark.parametrize(("node", "kwargs"), CASES, ids=IDS)
+def test_rgb_is_adjusted_on_every_channel(node, kwargs):
+    src = image(3)
+
+    out = node._process(src, **kwargs)
+
+    assert out.shape == src.shape
+    assert not torch.equal(out, src)
+
+
+@pytest.mark.parametrize(("node", "kwargs"), CASES, ids=IDS)
+def test_rgba_keeps_alpha_untouched(node, kwargs):
+    src = image(4)
+
+    out = node._process(src, **kwargs)
+
+    assert out.shape[-1] == 4
+    assert torch.equal(out[..., 3], src[..., 3])
+
+
+@pytest.mark.parametrize(("node", "kwargs"), CASES, ids=IDS)
+def test_colour_channels_still_change(node, kwargs):
+    src = image(4)
+
+    out = node._process(src, **kwargs)
+
+    assert not torch.equal(out[..., :3], src[..., :3])
+
+
+@pytest.mark.parametrize(("node", "kwargs"), CASES, ids=IDS)
+def test_transparent_pixels_stay_transparent(node, kwargs):
+    src = image(4, alpha=0.0)
+
+    out = node._process(src, **kwargs)
+
+    assert torch.all(out[..., 3] == 0.0)
+
+
+@pytest.mark.parametrize(("node", "kwargs"), CASES, ids=IDS)
+def test_does_not_mutate_input(node, kwargs):
+    src = image(4)
+    before = src.clone()
+
+    node._process(src, **kwargs)
+
+    assert torch.equal(src, before)