diff --git a/src/py/flwr/common/config.py b/src/py/flwr/common/config.py
index 8eb5f60b9d8..5c647b572db 100644
--- a/src/py/flwr/common/config.py
+++ b/src/py/flwr/common/config.py
@@ -141,6 +141,23 @@ def flatten_dict(
     return dict(items)
 
 
+def unflatten_dict(flat_dict: Dict[str, Any]) -> Dict[str, Any]:
+    """Unflatten a dict with keys containing separators into a nested dict."""
+    unflattened_dict: Dict[str, Any] = {}
+    separator: str = "."
+
+    for key, value in flat_dict.items():
+        parts = key.split(separator)
+        d = unflattened_dict
+        for part in parts[:-1]:
+            if part not in d:
+                d[part] = {}
+            d = d[part]
+        d[parts[-1]] = value
+
+    return unflattened_dict
+
+
 def parse_config_args(
     config: Optional[List[str]],
     separator: str = ",",
diff --git a/src/py/flwr/common/config_test.py b/src/py/flwr/common/config_test.py
index 52dcc0f9121..0e6a5bb8cb9 100644
--- a/src/py/flwr/common/config_test.py
+++ b/src/py/flwr/common/config_test.py
@@ -30,6 +30,7 @@
     get_project_config,
     get_project_dir,
     parse_config_args,
+    unflatten_dict,
 )
 
 # Mock constants
@@ -229,6 +230,13 @@ def test_flatten_dict() -> None:
     assert flatten_dict(raw_dict) == expected
 
 
+def test_unflatten_dict() -> None:
+    """Test unflatten_dict with a flat dictionary."""
+    raw_dict = {"a.b.c": "d", "e": "f"}
+    expected = {"a": {"b": {"c": "d"}}, "e": "f"}
+    assert unflatten_dict(raw_dict) == expected
+
+
 def test_parse_config_args_none() -> None:
     """Test parse_config_args with None as input."""
     assert not parse_config_args(None)