diff --git a/CHANGELOG.md b/CHANGELOG.md
index c7eb7308..36ffea24 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Changed
 * Added scipy to optional dependencies to be compatible with HDMF 4.0. @rly [#261](https://github.com/hdmf-dev/hdmf-zarr/pull/261)
+* Added warning in NWBZarrIO if writing file name that does not end in ".nwb.zarr". @stephprince [#265](https://github.com/hdmf-dev/hdmf-zarr/pull/265)
 
 ## 0.11.0 (January 17, 2025)
 
diff --git a/src/hdmf_zarr/nwb.py b/src/hdmf_zarr/nwb.py
index 97a62573..90079315 100644
--- a/src/hdmf_zarr/nwb.py
+++ b/src/hdmf_zarr/nwb.py
@@ -1,5 +1,6 @@
 """Module with Zarr backend for NWB for integration with PyNWB"""
 
+import warnings
 from pathlib import Path
 from .backend import ZarrIO, SUPPORTED_ZARR_STORES
 
@@ -42,6 +43,11 @@ def __init__(self, **kwargs):
         if mode in io_modes_that_create_file or manager is not None or extensions is not None:
             load_namespaces = False
 
+        if mode in io_modes_that_create_file and not str(path).endswith('.nwb.zarr'):
+            warnings.warn(f"The file path provided: {path} does not end in '.nwb.zarr'. "
+                           "It is recommended that NWB files using the Zarr backend use "
+                           "the '.nwb.zarr' extension", UserWarning)
+
         if load_namespaces:
             tm = get_type_map()
             super().load_namespaces(tm, path, storage_options)
diff --git a/tests/unit/test_nwbzarrio.py b/tests/unit/test_nwbzarrio.py
index c54d7225..f21fc0e2 100644
--- a/tests/unit/test_nwbzarrio.py
+++ b/tests/unit/test_nwbzarrio.py
@@ -4,6 +4,9 @@
 import shutil
 from datetime import datetime
 from dateutil.tz import tzlocal
+from pathlib import Path
+
+from hdmf.testing import TestCase
 
 try:
     from pynwb import NWBFile
@@ -14,18 +17,11 @@
 
 
 @unittest.skipIf(not PYNWB_AVAILABLE, "PyNWB not installed")
-class TestNWBZarrIO(unittest.TestCase):
+class TestNWBZarrIO(TestCase):
 
     def setUp(self):
-        self.filepath = "test_io.zarr"
-
-    def tearDown(self):
-        if os.path.exists(self.filepath):
-            shutil.rmtree(self.filepath)
-
-    def write_test_file(self):
-        # Create the NWBFile
-        nwbfile = NWBFile(
+        self.filepath = "test_io.nwb.zarr"
+        self.nwbfile = NWBFile(
             session_description="my first synthetic recording",
             identifier="EXAMPLE_ID",
             session_start_time=datetime.now(tzlocal()),
@@ -35,11 +31,33 @@ def write_test_file(self):
             experiment_description="I went on an adventure with thirteen dwarves to reclaim vast treasures.",
             session_id="LONELYMTN",
         )
-
         # Create a device
-        nwbfile.create_device(name="array", description="the best array", manufacturer="Probe Company 9000")
+        self.nwbfile.create_device(name="array", description="the best array", manufacturer="Probe Company 9000")
+
+    def tearDown(self):
+        if os.path.exists(self.filepath):
+            shutil.rmtree(self.filepath)
+
+    def write_test_file(self):
         with NWBZarrIO(path=self.filepath, mode="w") as io:
-            io.write(nwbfile)
+            io.write(self.nwbfile)
+
+    def test_file_extension_warning(self):
+        """Test that a warning is raised when the file extension is not .nwb.zarr"""
+        wrong_filepath = Path(self.filepath).with_suffix('.h5')
+
+        msg = (f"The file path provided: {wrong_filepath} does not end in '.nwb.zarr'. "
+                "It is recommended that NWB files using the Zarr backend use the '.nwb.zarr' extension")
+
+        with self.assertWarnsWith(UserWarning, msg):
+            with NWBZarrIO(path=wrong_filepath, mode="w") as io:
+                io.write(self.nwbfile)
+
+        # should not warn on read or append
+        with NWBZarrIO(wrong_filepath, 'r') as io:
+            io.read()
+        with NWBZarrIO(wrong_filepath, 'a') as io:
+            io.read()
 
     def test_read_nwb(self):
         """