diff --git a/src/tests/test_modify_entry_validation.py b/src/tests/test_modify_entry_validation.py
new file mode 100644
index 00000000..7c210a66
--- /dev/null
+++ b/src/tests/test_modify_entry_validation.py
@@ -0,0 +1,107 @@
+import sys
+from pathlib import Path
+from tempfile import TemporaryDirectory
+import pytest
+
+# Add source directory to path
+sys.path.append(str(Path(__file__).resolve().parents[1]))
+
+from seedpass.core.entry_management import EntryManager
+from seedpass.core.entry_types import EntryType
+from seedpass.core.backup import BackupManager
+from seedpass.core.config_manager import ConfigManager
+from helpers import create_vault, TEST_SEED, TEST_PASSWORD
+
+
+@pytest.fixture
+def entry_manager():
+    """Fixture to set up an EntryManager with a temporary vault."""
+    with TemporaryDirectory() as tmpdir:
+        vault, _ = create_vault(Path(tmpdir), TEST_SEED, TEST_PASSWORD)
+        cfg_mgr = ConfigManager(vault, Path(tmpdir))
+        backup_mgr = BackupManager(Path(tmpdir), cfg_mgr)
+        yield EntryManager(vault, backup_mgr)
+
+
+@pytest.mark.parametrize(
+    "entry_type, setup_func, invalid_kwargs, expected_msg_part",
+    [
+        (
+            EntryType.PASSWORD,
+            lambda em: em.add_entry("Pass", 12),
+            {"period": 30},  # 'period' is for TOTP, not Password
+            "does not support fields: period",
+        ),
+        (
+            EntryType.TOTP,
+            lambda em: em.add_totp("TOTP", TEST_SEED),
+            {"username": "user"},  # 'username' is for Password, not TOTP
+            "does not support fields: username",
+        ),
+        (
+            EntryType.KEY_VALUE,
+            lambda em: em.add_key_value("KV", "k", "v"),
+            {"url": "http://example.com"},  # 'url' is for Password, not KeyValue
+            "does not support fields: url",
+        ),
+        (
+            EntryType.MANAGED_ACCOUNT,
+            lambda em: em.add_managed_account("MA", TEST_SEED),
+            {"key": "new_key"},  # 'key' is for KeyValue, not ManagedAccount
+            "does not support fields: key",
+        ),
+        (
+            EntryType.SSH,
+            lambda em: em.add_ssh_key("SSH", TEST_SEED),
+            {"value": "some_val"},  # 'value' is for KeyValue/ManagedAccount, not SSH
+            "does not support fields: value",
+        ),
+        (
+            EntryType.PGP,
+            lambda em: em.add_pgp_key("PGP", TEST_SEED),
+            {"username": "pgp_user"},
+            "does not support fields: username",
+        ),
+        (
+            EntryType.NOSTR,
+            lambda em: em.add_nostr_key("Nostr", TEST_SEED),
+            {"period": 60},
+            "does not support fields: period",
+        ),
+        (
+            EntryType.SEED,
+            lambda em: em.add_seed("Seed", TEST_SEED),
+            {"url": "seed_url"},
+            "does not support fields: url",
+        ),
+    ],
+)
+def test_modify_entry_invalid_fields(
+    entry_manager, entry_type, setup_func, invalid_kwargs, expected_msg_part
+):
+    """Test that modify_entry raises ValueError for invalid fields based on EntryType."""
+    # Setup entry
+    if entry_type == EntryType.TOTP:
+         # add_totp returns a URI string, need to fix the index manually or check implementation
+         # Checking implementation: add_totp returns URI string, but index is predictable (0)
+         # However, we should verify the index.
+         # For simplicity, we assume index 0 as it's the first entry.
+         setup_func(entry_manager)
+         index = 0
+    elif entry_type == EntryType.PASSWORD:
+         index = setup_func(entry_manager)
+    else:
+         index = setup_func(entry_manager)
+
+    # Verify entry exists and has correct type
+    entry = entry_manager.retrieve_entry(index)
+    assert entry is not None
+    # Handle legacy 'kind' vs 'type'
+    actual_type = entry.get("type", entry.get("kind"))
+    assert actual_type == entry_type.value
+
+    # Attempt modification with invalid fields
+    with pytest.raises(ValueError) as excinfo:
+        entry_manager.modify_entry(index, **invalid_kwargs)
+
+    assert expected_msg_part in str(excinfo.value)