diff --git a/app/service/validation.py b/app/service/validation.py
index 439020fb..85658029 100644
--- a/app/service/validation.py
+++ b/app/service/validation.py
@@ -239,4 +239,36 @@ def validate_bulk_import_data(data: dict[str, Any]) -> None:
     if not data:
         raise HTTPException(status_code=status.HTTP_204_NO_CONTENT)
 
+    validate_metadata_values_are_strings(data)
     validate_entity_relationships(data)
+
+
+def _validate_values_are_strings(value: Any) -> None:
+    """
+    Recursively validates that all single values are strings.
+
+    :param Any value: The value to be validated.
+    :raises ValidationError: raised if any single value is not a string.
+    """
+    if isinstance(value, list):
+        for v in value:
+            _validate_values_are_strings(v)
+    elif not isinstance(value, str):
+        raise ValidationError("Metadata values should be strings")
+
+
+def validate_metadata_values_are_strings(data: dict[str, Any]) -> None:
+    """
+    Validates any metadata in the data.
+
+    :param dict[str, Any] data: The data object to be validated.
+    """
+    metadata_values = [
+        value
+        for entity in data.values()
+        if entity is not None
+        for e in entity
+        for value in e.get("metadata", {}).values()
+    ]
+
+    _validate_values_are_strings(metadata_values)
diff --git a/pyproject.toml b/pyproject.toml
index 0f5ba2ff..cc17c644 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "admin_backend"
-version = "2.17.19"
+version = "2.17.20"
 description = ""
 authors = ["CPR-dev-team <tech@climatepolicyradar.org>"]
 packages = [{ include = "app" }, { include = "tests" }]
diff --git a/tests/unit_tests/routers/bulk_import/test_bulk_import.py b/tests/unit_tests/routers/bulk_import/test_bulk_import.py
index 13e7360f..91d560cf 100644
--- a/tests/unit_tests/routers/bulk_import/test_bulk_import.py
+++ b/tests/unit_tests/routers/bulk_import/test_bulk_import.py
@@ -118,3 +118,20 @@ def test_bulk_import_documents_when_no_family(
 
     assert response.status_code == status.HTTP_400_BAD_REQUEST
     assert response.json().get("detail") == "No entity with id test.new.family.0 found"
+
+
+def test_bulk_import_when_metadata_contains_non_string_values(
+    client: TestClient, superuser_header_token
+):
+    json_input = build_json_file(
+        {"families": [{**default_family, "metadata": {"key": [1]}}]}
+    )
+
+    response = client.post(
+        "/api/v1/bulk-import/test",
+        files={"data": json_input},
+        headers=superuser_header_token,
+    )
+
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+    assert response.json().get("detail") == "Metadata values should be strings"
diff --git a/tests/unit_tests/service/validation/test_metadata_validation.py b/tests/unit_tests/service/validation/test_metadata_validation.py
new file mode 100644
index 00000000..0d3ea5e5
--- /dev/null
+++ b/tests/unit_tests/service/validation/test_metadata_validation.py
@@ -0,0 +1,38 @@
+import pytest
+
+from app.errors import ValidationError
+from app.service.validation import validate_metadata_values_are_strings
+
+
+@pytest.mark.parametrize(
+    "test_data",
+    [
+        {"entity1": [{"metadata": {"key1": ["value"], "key2": [""]}}]},
+        {"entity2": [{"other_key": {"key1": ["value"]}}]},
+        {"entity3": [{}]},
+        {"entity4": []},
+        {"entity5": ""},
+        {"entity6": None},
+        {},
+    ],
+)
+def test_validate_metadata_when_ok(test_data):
+
+    validate_metadata_values_are_strings(test_data)
+
+
+@pytest.mark.parametrize(
+    "test_data",
+    [
+        {"entity": [{"metadata": {"key": [1]}}]},
+        {"entity": [{"metadata": {"key": [1]}}]},
+        {"entity": [{"metadata": {"key": 1}}]},
+        {"entity": [{"metadata": {"key": [None]}}]},
+        {"entity": [{"metadata": {"key": None}}]},
+    ],
+)
+def test_validate_metadata_throws_exception_when_non_string_values_present(test_data):
+
+    with pytest.raises(ValidationError) as e:
+        validate_metadata_values_are_strings(test_data)
+    assert "Metadata values should be strings" == e.value.message