diff --git a/bigquery/google/cloud/bigquery/model.py b/bigquery/google/cloud/bigquery/model.py
index 8b29e4008558..4049a9232467 100644
--- a/bigquery/google/cloud/bigquery/model.py
+++ b/bigquery/google/cloud/bigquery/model.py
@@ -268,6 +268,9 @@ def from_api_repr(cls, resource):
             google.cloud.bigquery.model.Model: Model parsed from ``resource``.
         """
         this = cls(None)
+        # Keep a reference to the resource as a workaround to find unknown
+        # field values.
+        this._properties = resource
 
         # Convert from millis-from-epoch to timestamp well-known type.
         # TODO: Remove this hack once CL 238585470 hits prod.
@@ -279,12 +282,9 @@ def from_api_repr(cls, resource):
             start_time = datetime_helpers.from_microseconds(1e3 * float(start_time))
             training_run["startTime"] = datetime_helpers.to_rfc3339(start_time)
 
-        this._proto = json_format.ParseDict(resource, types.Model())
-        for key in six.itervalues(cls._PROPERTY_TO_API_FIELD):
-            # Leave missing keys unset. This allows us to use setdefault in the
-            # getters where we want a default value other than None.
-            if key in resource:
-                this._properties[key] = resource[key]
+        this._proto = json_format.ParseDict(
+            resource, types.Model(), ignore_unknown_fields=True
+        )
         return this
 
     def _build_resource(self, filter_fields):
@@ -304,6 +304,7 @@ class ModelReference(object):
 
     def __init__(self):
         self._proto = types.ModelReference()
+        self._properties = {}
 
     @property
     def project(self):
@@ -342,7 +343,12 @@ def from_api_repr(cls, resource):
                 Model reference parsed from ``resource``.
         """
         ref = cls()
-        ref._proto = json_format.ParseDict(resource, types.ModelReference())
+        # Keep a reference to the resource as a workaround to find unknown
+        # field values.
+        ref._properties = resource
+        ref._proto = json_format.ParseDict(
+            resource, types.ModelReference(), ignore_unknown_fields=True
+        )
         return ref
 
     @classmethod
diff --git a/bigquery/tests/unit/model/test_model.py b/bigquery/tests/unit/model/test_model.py
index 2086c333486d..b6d9756e15fe 100644
--- a/bigquery/tests/unit/model/test_model.py
+++ b/bigquery/tests/unit/model/test_model.py
@@ -165,6 +165,22 @@ def test_from_api_repr_w_minimal_resource(target_class):
     assert len(got.label_columns) == 0
 
 
+def test_from_api_repr_w_unknown_fields(target_class):
+    from google.cloud.bigquery import ModelReference
+
+    resource = {
+        "modelReference": {
+            "projectId": "my-project",
+            "datasetId": "my_dataset",
+            "modelId": "my_model",
+        },
+        "thisFieldIsNotInTheProto": "just ignore me",
+    }
+    got = target_class.from_api_repr(resource)
+    assert got.reference == ModelReference.from_string("my-project.my_dataset.my_model")
+    assert got._properties is resource
+
+
 @pytest.mark.parametrize(
     "resource,filter_fields,expected",
     [
diff --git a/bigquery/tests/unit/model/test_model_reference.py b/bigquery/tests/unit/model/test_model_reference.py
index 0145c76f6ad0..ff1d1df7d499 100644
--- a/bigquery/tests/unit/model/test_model_reference.py
+++ b/bigquery/tests/unit/model/test_model_reference.py
@@ -37,6 +37,20 @@ def test_from_api_repr(target_class):
     assert got.path == "/projects/my-project/datasets/my_dataset/models/my_model"
 
 
+def test_from_api_repr_w_unknown_fields(target_class):
+    resource = {
+        "projectId": "my-project",
+        "datasetId": "my_dataset",
+        "modelId": "my_model",
+        "thisFieldIsNotInTheProto": "just ignore me",
+    }
+    got = target_class.from_api_repr(resource)
+    assert got.project == "my-project"
+    assert got.dataset_id == "my_dataset"
+    assert got.model_id == "my_model"
+    assert got._properties is resource
+
+
 def test_to_api_repr(target_class):
     ref = target_class.from_string("my-project.my_dataset.my_model")
     got = ref.to_api_repr()