diff --git a/qlib/contrib/model/catboost_model.py b/qlib/contrib/model/catboost_model.py
index 4fc1c6f8934..27c645a88e1 100644
--- a/qlib/contrib/model/catboost_model.py
+++ b/qlib/contrib/model/catboost_model.py
@@ -31,10 +31,12 @@ def fit(
         num_boost_round=1000,
         early_stopping_rounds=50,
         verbose_eval=20,
-        evals_result=dict(),
+        evals_result=None,
         reweighter=None,
         **kwargs,
     ):
+        if evals_result is None:
+            evals_result = {}
         df_train, df_valid = dataset.prepare(
             ["train", "valid"],
             col_set=["feature", "label"],
@@ -73,9 +75,9 @@ def fit(
         # train the model
         self.model.fit(train_pool, eval_set=valid_pool, use_best_model=True, **kwargs)
 
-        evals_result = self.model.get_evals_result()
-        evals_result["train"] = list(evals_result["learn"].values())[0]
-        evals_result["valid"] = list(evals_result["validation"].values())[0]
+        model_evals_result = self.model.get_evals_result()
+        evals_result["train"] = list(model_evals_result["learn"].values())[0]
+        evals_result["valid"] = list(model_evals_result["validation"].values())[0]
 
     def predict(self, dataset: DatasetH, segment: Union[Text, slice] = "test"):
         if self.model is None:
diff --git a/qlib/contrib/model/xgboost.py b/qlib/contrib/model/xgboost.py
index 634259aab14..64d20de5322 100755
--- a/qlib/contrib/model/xgboost.py
+++ b/qlib/contrib/model/xgboost.py
@@ -26,10 +26,12 @@ def fit(
         num_boost_round=1000,
         early_stopping_rounds=50,
         verbose_eval=20,
-        evals_result=dict(),
+        evals_result=None,
         reweighter=None,
         **kwargs,
     ):
+        if evals_result is None:
+            evals_result = {}
         df_train, df_valid = dataset.prepare(
             ["train", "valid"],
             col_set=["feature", "label"],
diff --git a/tests/model/test_contrib_model_evals_result.py b/tests/model/test_contrib_model_evals_result.py
new file mode 100644
index 00000000000..6cd3a263546
--- /dev/null
+++ b/tests/model/test_contrib_model_evals_result.py
@@ -0,0 +1,117 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+import inspect
+import unittest
+from unittest import mock
+
+try:
+    import numpy as np
+except ImportError:
+    np = None
+
+try:
+    import qlib.contrib.model.catboost_model as catboost_model
+except ImportError:
+    catboost_model = None
+
+try:
+    import qlib.contrib.model.xgboost as xgboost_model
+except ImportError:
+    xgboost_model = None
+
+
+class _Column:
+    def __init__(self, values):
+        self.values = np.asarray(values)
+
+
+class _Frame:
+    empty = False
+
+    def __init__(self):
+        self._columns = {
+            "feature": _Column([[1.0], [2.0]]),
+            "label": _Column([[0.0], [1.0]]),
+        }
+
+    def __getitem__(self, key):
+        return self._columns[key]
+
+
+class _Dataset:
+    def prepare(self, *args, **kwargs):
+        return _Frame(), _Frame()
+
+
+@unittest.skipUnless(catboost_model is not None, "CatBoost dependencies are not installed")
+class TestCatBoostModelEvalsResult(unittest.TestCase):
+    def test_fit_updates_caller_evals_result(self):
+        class FakeCatBoost:
+            def fit(self, *args, **kwargs):
+                pass
+
+            def get_evals_result(self):
+                return {
+                    "learn": {"RMSE": [0.4, 0.2]},
+                    "validation": {"RMSE": [0.5, 0.3]},
+                }
+
+        evals_result = {"existing": [1]}
+        model = catboost_model.CatBoostModel()
+        with mock.patch.object(catboost_model, "Pool"), mock.patch.object(
+            catboost_model, "CatBoost", return_value=FakeCatBoost()
+        ), mock.patch.object(catboost_model, "get_gpu_device_count", return_value=0):
+            model.fit(_Dataset(), evals_result=evals_result)
+
+        self.assertEqual(evals_result["train"], [0.4, 0.2])
+        self.assertEqual(evals_result["valid"], [0.5, 0.3])
+        self.assertEqual(evals_result["existing"], [1])
+
+    def test_evals_result_default_is_not_mutable(self):
+        default = inspect.signature(catboost_model.CatBoostModel.fit).parameters["evals_result"].default
+        self.assertIsNone(default)
+
+
+@unittest.skipUnless(xgboost_model is not None, "XGBoost dependencies are not installed")
+class TestXGBModelEvalsResult(unittest.TestCase):
+    def test_fit_updates_caller_evals_result(self):
+        def train(*args, evals_result, **kwargs):
+            evals_result.update({"train": {"rmse": [0.4]}, "valid": {"rmse": [0.5]}})
+            return object()
+
+        evals_result = {"existing": [1]}
+        model = xgboost_model.XGBModel()
+        with mock.patch.object(xgboost_model.xgb, "DMatrix", return_value=object()), mock.patch.object(
+            xgboost_model.xgb, "train", side_effect=train
+        ):
+            model.fit(_Dataset(), evals_result=evals_result)
+
+        self.assertEqual(evals_result["train"], [0.4])
+        self.assertEqual(evals_result["valid"], [0.5])
+        self.assertEqual(evals_result["existing"], [1])
+
+    def test_fit_uses_a_fresh_default_evals_result(self):
+        captured = []
+
+        def train(*args, evals_result, **kwargs):
+            captured.append(evals_result)
+            evals_result.update({"train": {"rmse": [0.4]}, "valid": {"rmse": [0.5]}})
+            return object()
+
+        model = xgboost_model.XGBModel()
+        with mock.patch.object(xgboost_model.xgb, "DMatrix", return_value=object()), mock.patch.object(
+            xgboost_model.xgb, "train", side_effect=train
+        ):
+            model.fit(_Dataset())
+            model.fit(_Dataset())
+
+        self.assertIsNot(captured[0], captured[1])
+
+    def test_evals_result_default_is_not_mutable(self):
+        default = inspect.signature(xgboost_model.XGBModel.fit).parameters["evals_result"].default
+        self.assertIsNone(default)
+
+
+if __name__ == "__main__":
+    unittest.main()