diff --git a/tests/test_case_sensitivity.py b/tests/test_case_sensitivity.py
new file mode 100644
index 0000000..1398d0d
--- /dev/null
+++ b/tests/test_case_sensitivity.py
@@ -0,0 +1,112 @@
+"""Tests for case-insensitive username/organization filtering."""
+
+import pytest
+from unittest.mock import Mock
+
+from github_backup import github_backup
+
+
+class TestCaseSensitivity:
+    """Test suite for case-insensitive username matching in filter_repositories."""
+
+    def test_filter_repositories_case_insensitive_user(self):
+        """Should filter repositories case-insensitively for usernames.
+
+        Reproduces issue #198 where typing 'iamrodos' fails to match
+        repositories with owner.login='Iamrodos' (the canonical case from GitHub API).
+        """
+        # Simulate user typing lowercase username
+        args = Mock()
+        args.user = "iamrodos"  # lowercase (what user typed)
+        args.repository = None
+        args.name_regex = None
+        args.languages = None
+        args.exclude = None
+        args.fork = False
+        args.private = False
+        args.public = False
+        args.all = True
+
+        # Simulate GitHub API returning canonical case
+        repos = [
+            {
+                "name": "repo1",
+                "owner": {"login": "Iamrodos"},  # Capital I (canonical from API)
+                "private": False,
+                "fork": False,
+            },
+            {
+                "name": "repo2",
+                "owner": {"login": "Iamrodos"},
+                "private": False,
+                "fork": False,
+            },
+        ]
+
+        filtered = github_backup.filter_repositories(args, repos)
+
+        # Should match despite case difference
+        assert len(filtered) == 2
+        assert filtered[0]["name"] == "repo1"
+        assert filtered[1]["name"] == "repo2"
+
+    def test_filter_repositories_case_insensitive_org(self):
+        """Should filter repositories case-insensitively for organizations.
+
+        Tests the example from issue #198 where 'prai-org' doesn't match 'PRAI-Org'.
+        """
+        args = Mock()
+        args.user = "prai-org"  # lowercase (what user typed)
+        args.repository = None
+        args.name_regex = None
+        args.languages = None
+        args.exclude = None
+        args.fork = False
+        args.private = False
+        args.public = False
+        args.all = True
+
+        repos = [
+            {
+                "name": "repo1",
+                "owner": {"login": "PRAI-Org"},  # Different case (canonical from API)
+                "private": False,
+                "fork": False,
+            },
+        ]
+
+        filtered = github_backup.filter_repositories(args, repos)
+
+        # Should match despite case difference
+        assert len(filtered) == 1
+        assert filtered[0]["name"] == "repo1"
+
+    def test_filter_repositories_case_variations(self):
+        """Should handle various case combinations correctly."""
+        args = Mock()
+        args.user = "TeSt-UsEr"  # Mixed case
+        args.repository = None
+        args.name_regex = None
+        args.languages = None
+        args.exclude = None
+        args.fork = False
+        args.private = False
+        args.public = False
+        args.all = True
+
+        repos = [
+            {"name": "repo1", "owner": {"login": "test-user"}, "private": False, "fork": False},
+            {"name": "repo2", "owner": {"login": "TEST-USER"}, "private": False, "fork": False},
+            {"name": "repo3", "owner": {"login": "TeSt-UsEr"}, "private": False, "fork": False},
+            {"name": "repo4", "owner": {"login": "other-user"}, "private": False, "fork": False},
+        ]
+
+        filtered = github_backup.filter_repositories(args, repos)
+
+        # Should match first 3 (all case variations of same user)
+        assert len(filtered) == 3
+        assert set(r["name"] for r in filtered) == {"repo1", "repo2", "repo3"}
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])