diff --git a/rest_framework/renderers.py b/rest_framework/renderers.py
index 8e8c3a9b3..23add173d 100644
--- a/rest_framework/renderers.py
+++ b/rest_framework/renderers.py
@@ -9,6 +9,7 @@ REST framework also provides an HTML renderer that renders the browsable API.
 
 import base64
 import contextlib
+import datetime
 from urllib import parse
 
 from django import forms
@@ -1056,6 +1057,7 @@ class OpenAPIRenderer(BaseRenderer):
             def ignore_aliases(self, data):
                 return True
         Dumper.add_representer(SafeString, Dumper.represent_str)
+        Dumper.add_representer(datetime.timedelta, encoders.CustomScalar.represent_timedelta)
         return yaml.dump(data, default_flow_style=False, sort_keys=False, Dumper=Dumper).encode('utf-8')
 
 
diff --git a/rest_framework/utils/encoders.py b/rest_framework/utils/encoders.py
index 35a89eb09..aa4542286 100644
--- a/rest_framework/utils/encoders.py
+++ b/rest_framework/utils/encoders.py
@@ -65,3 +65,14 @@ class JSONEncoder(json.JSONEncoder):
         elif hasattr(obj, '__iter__'):
             return tuple(item for item in obj)
         return super().default(obj)
+
+
+class CustomScalar:
+    """
+    CustomScalar that knows how to encode timedelta that renderer
+    can understand.
+    """
+    @classmethod
+    def represent_timedelta(cls, dumper, data):
+        value = str(data.total_seconds())
+        return dumper.represent_scalar('tag:yaml.org,2002:str', value)