diff --git a/src/neuroconv/datainterfaces/ophys/miniscope/miniscopeimagingdatainterface.py b/src/neuroconv/datainterfaces/ophys/miniscope/miniscopeimagingdatainterface.py
index 9c524078b..04f563dd9 100644
--- a/src/neuroconv/datainterfaces/ophys/miniscope/miniscopeimagingdatainterface.py
+++ b/src/neuroconv/datainterfaces/ophys/miniscope/miniscopeimagingdatainterface.py
@@ -433,6 +433,7 @@ def add_to_nwbfile(
         self,
         nwbfile: NWBFile,
         metadata: dict | None = None,
+        *args,  # TODO: change to * (keyword only) on or after August 2026
         photon_series_type: Literal["TwoPhotonSeries", "OnePhotonSeries"] = "OnePhotonSeries",
         **kwargs,
     ):
@@ -441,6 +442,33 @@ def add_to_nwbfile(
 
         This method adds the Miniscope device and then delegates to the parent class.
         """
+        # Handle deprecated positional arguments
+        if args:
+            import warnings
+
+            parameter_names = [
+                "photon_series_type",
+            ]
+            num_positional_args_before_args = 2  # nwbfile, metadata
+            if len(args) > len(parameter_names):
+                raise TypeError(
+                    f"add_to_nwbfile() takes at most {len(parameter_names) + num_positional_args_before_args} positional arguments but "
+                    f"{len(args) + num_positional_args_before_args} were given. "
+                    "Note: Positional arguments are deprecated and will be removed on or after August 2026. "
+                    "Please use keyword arguments."
+                )
+            positional_values = dict(zip(parameter_names, args))
+            passed_as_positional = list(positional_values.keys())
+            warnings.warn(
+                "Passing arguments positionally to MiniscopeImagingInterface.add_to_nwbfile() is deprecated "
+                "and will be removed on or after August 2026. "
+                f"The following arguments were passed positionally: {passed_as_positional}. "
+                "Please use keyword arguments instead.",
+                FutureWarning,
+                stacklevel=2,
+            )
+            photon_series_type = positional_values.get("photon_series_type", photon_series_type)
+
         from ndx_miniscope.utils import add_miniscope_device
 
         # Add Miniscope device - required for proper ndx_miniscope.Miniscope device type
diff --git a/tests/test_minimal/test_keyword_only_arguments.py b/tests/test_minimal/test_keyword_only_arguments.py
new file mode 100644
index 000000000..47531478d
--- /dev/null
+++ b/tests/test_minimal/test_keyword_only_arguments.py
@@ -0,0 +1,41 @@
+"""Tests to enforce keyword-only argument conventions for add_to_nwbfile methods.
+
+These tests ensure that all interface add_to_nwbfile methods enforce keyword-only arguments
+after nwbfile and metadata. Only nwbfile and metadata should be positional.
+
+During the deprecation period (before August 2026), methods use *args with FutureWarning.
+After the deprecation period, methods should use bare * for keyword-only enforcement.
+
+See the developer style guide for details on the convention.
+"""
+
+import inspect
+
+import pytest
+
+from neuroconv.datainterfaces import interface_list
+
+
+@pytest.mark.parametrize(
+    "interface_class",
+    interface_list,
+    ids=lambda cls: cls.__name__,
+)
+def test_add_to_nwbfile_only_nwbfile_metadata_positional(interface_class):
+    """Only nwbfile and metadata should be positional in add_to_nwbfile."""
+    if "add_to_nwbfile" not in interface_class.__dict__:
+        pytest.skip(f"{interface_class.__name__} does not override add_to_nwbfile")
+
+    add_to_nwbfile_method = getattr(interface_class, "add_to_nwbfile")
+    sig = inspect.signature(add_to_nwbfile_method)
+
+    # No add_to_nwbfile uses POSITIONAL_ONLY (/), so POSITIONAL_OR_KEYWORD means "can be passed positionally"
+    can_be_passed_positionally = lambda param: param.kind == inspect.Parameter.POSITIONAL_OR_KEYWORD
+    positional_params = {name for name, param in sig.parameters.items() if can_be_passed_positionally(param)}
+
+    allowed_positional_params = {"self", "nwbfile", "metadata"}
+    assert positional_params == allowed_positional_params, (
+        f"{interface_class.__name__}.add_to_nwbfile() positional parameters are {positional_params}, "
+        f"expected {allowed_positional_params}. "
+        f"All other parameters should be keyword-only (use * or *args)."
+    )