diff --git a/bravado_core/param.py b/bravado_core/param.py
index d6100e60..108fbc04 100644
--- a/bravado_core/param.py
+++ b/bravado_core/param.py
@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+import datetime
 import logging
 from functools import partial
 
@@ -23,12 +24,17 @@
 }
 
 
+def default_handler(x):
+    if isinstance(x, datetime.datetime) or isinstance(x, datetime.date):
+        return x.isoformat()
+
+
 def stringify_body(value):
     """Json dump the value to string if not already in string
     """
     if not value or isinstance(value, six.string_types):
         return value
-    return json.dumps(value)
+    return json.dumps(value, default=default_handler)
 
 
 class Param(object):
@@ -141,7 +147,7 @@ def marshal_param(param, value, request):
             request.setdefault('data', {})[param.name] = value
     elif location == 'body':
         request['headers']['Content-Type'] = APP_JSON
-        request['data'] = json.dumps(value)
+        request['data'] = json.dumps(value, default=default_handler)
     else:
         raise SwaggerMappingError(
             "Don't know how to marshal_param with location {0}".
diff --git a/tests/param/marshal_param_test.py b/tests/param/marshal_param_test.py
index 7f0ba250..0c1fb105 100644
--- a/tests/param/marshal_param_test.py
+++ b/tests/param/marshal_param_test.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import copy
+import datetime
 
 import pytest
 from mock import Mock
@@ -159,6 +160,46 @@ def test_body(empty_swagger_spec, param_spec):
     assert APP_JSON == request['headers']['Content-Type']
 
 
+def test_body_nested_date(empty_swagger_spec, param_spec):
+    now = datetime.date.today()
+    now_param = {'updated_at': now}
+    now_str = '{"updated_at": "' + now.isoformat() + '"}'
+    param_spec['in'] = 'body'
+    param_spec['schema'] = {
+        'type': 'object'
+    }
+    del param_spec['type']
+    del param_spec['format']
+    param = Param(empty_swagger_spec, Mock(spec=Operation), param_spec)
+    request = {
+        'headers': {
+        }
+    }
+    marshal_param(param, now_param, request)
+    assert now_str == request['data']
+    assert APP_JSON == request['headers']['Content-Type']
+
+
+def test_body_nested_datetime(empty_swagger_spec, param_spec):
+    now = datetime.datetime.utcnow()
+    now_param = {"updated_at": now}
+    now_str = '{"updated_at": "' + now.isoformat() + '"}'
+    param_spec['in'] = 'body'
+    param_spec['schema'] = {
+        'type': 'object'
+    }
+    del param_spec['type']
+    del param_spec['format']
+    param = Param(empty_swagger_spec, Mock(spec=Operation), param_spec)
+    request = {
+        'headers': {
+        }
+    }
+    marshal_param(param, now_param, request)
+    assert now_str == request['data']
+    assert APP_JSON == request['headers']['Content-Type']
+
+
 def test_formData_integer(empty_swagger_spec, param_spec):
     param_spec['in'] = 'formData'
     param = Param(empty_swagger_spec, Mock(spec=Operation), param_spec)
diff --git a/tests/param/stringify_body_test.py b/tests/param/stringify_body_test.py
index ce8922ee..261387cc 100644
--- a/tests/param/stringify_body_test.py
+++ b/tests/param/stringify_body_test.py
@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+import datetime
 import json
 
 from bravado_core.param import stringify_body
@@ -12,3 +13,19 @@ def test_stringify_body_converts_dict_to_str():
 
 def test_stringify_body_ignores_data_if_already_str():
     assert 'foo' == stringify_body('foo')
+
+
+def test_stringify_body_handles_date():
+    now = datetime.date.today()
+    now_str = '{"now": "' + now.isoformat() + '"}'
+    body = {'now': now}
+    body_str = stringify_body(body)
+    assert body_str == now_str
+
+
+def test_stringify_body_handles_datetime():
+    now = datetime.datetime.utcnow()
+    now_str = '{"now": "' + now.isoformat() + '"}'
+    body = {'now': now}
+    body_str = stringify_body(body)
+    assert body_str == now_str