diff --git a/src/betterproto/__init__.py b/src/betterproto/__init__.py
index b26ec4b..9a337c4 100644
--- a/src/betterproto/__init__.py
+++ b/src/betterproto/__init__.py
@@ -961,7 +961,15 @@ class Message(ABC):
                         output[cased_name] = value
                 elif field_is_repeated:
                     # Convert each item.
-                    value = [i.to_dict(casing, include_default_values) for i in value]
+                    cls = self._betterproto.cls_by_field[field_name]
+                    if cls == datetime:
+                        value = [_Timestamp.timestamp_to_json(i) for i in value]
+                    elif cls == timedelta:
+                        value = [_Duration.delta_to_json(i) for i in value]
+                    else:
+                        value = [
+                            i.to_dict(casing, include_default_values) for i in value
+                        ]
                     if value or include_default_values:
                         output[cased_name] = value
                 elif (
@@ -1042,8 +1050,18 @@ class Message(ABC):
                     v = getattr(self, field_name)
                     if isinstance(v, list):
                         cls = self._betterproto.cls_by_field[field_name]
-                        for item in value[key]:
-                            v.append(cls().from_dict(item))
+                        if cls == datetime:
+                            v = [
+                                datetime.fromisoformat(item.replace("Z", "+00:00"))
+                                for item in value[key]
+                            ]
+                        elif cls == timedelta:
+                            v = [
+                                timedelta(seconds=float(item[:-1]))
+                                for item in value[key]
+                            ]
+                        else:
+                            v = [cls().from_dict(item) for item in value[key]]
                     elif isinstance(v, datetime):
                         v = datetime.fromisoformat(value[key].replace("Z", "+00:00"))
                         setattr(self, field_name, v)
diff --git a/tests/inputs/repeated_duration_timestamp/repeated_duration_timestamp.json b/tests/inputs/repeated_duration_timestamp/repeated_duration_timestamp.json
new file mode 100644
index 0000000..6ce7b34
--- /dev/null
+++ b/tests/inputs/repeated_duration_timestamp/repeated_duration_timestamp.json
@@ -0,0 +1,4 @@
+{
+    "times": ["1972-01-01T10:00:20.021Z", "1972-01-01T10:00:20.021Z"],
+    "durations": ["1.200s", "1.200s"]
+}
diff --git a/tests/inputs/repeated_duration_timestamp/repeated_duration_timestamp.proto b/tests/inputs/repeated_duration_timestamp/repeated_duration_timestamp.proto
new file mode 100644
index 0000000..7b7bf36
--- /dev/null
+++ b/tests/inputs/repeated_duration_timestamp/repeated_duration_timestamp.proto
@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+import "google/protobuf/duration.proto";
+import "google/protobuf/timestamp.proto";
+
+
+message Test {
+    repeated google.protobuf.Timestamp times = 1;
+    repeated google.protobuf.Duration durations = 2;
+}
diff --git a/tests/inputs/repeated_duration_timestamp/test_repeated_duration_timestamp.py b/tests/inputs/repeated_duration_timestamp/test_repeated_duration_timestamp.py
new file mode 100644
index 0000000..b1b13e5
--- /dev/null
+++ b/tests/inputs/repeated_duration_timestamp/test_repeated_duration_timestamp.py
@@ -0,0 +1,9 @@
+from datetime import datetime, timedelta
+
+from tests.output_betterproto.repeated_duration_timestamp import Test
+
+
+def test_roundtrip():
+    message = Test()
+    message.times = [datetime.now(), datetime.now()]
+    message.durations = [timedelta(), timedelta()]