diff --git a/AUTHORS.rst b/AUTHORS.rst
index 43a4e4df..072321bb 100644
--- a/AUTHORS.rst
+++ b/AUTHORS.rst
@@ -135,4 +135,5 @@ Patches and Suggestions
 - David Pursehouse <david.pursehouse@gmail.com> @dpursehouse
 - Jon Parise
 - Alexander Karpinsky @homm86
-- Marc Schlaich @schlamar
\ No newline at end of file
+- Marc Schlaich @schlamar
+- Park Ilsu <daftonshady@gmail.com> @daftshady
diff --git a/requests/cookies.py b/requests/cookies.py
index f3ac64f0..ea56c065 100644
--- a/requests/cookies.py
+++ b/requests/cookies.py
@@ -392,15 +392,21 @@ def morsel_to_cookie(morsel):
     return c
 
 
-def cookiejar_from_dict(cookie_dict, cookiejar=None):
+def cookiejar_from_dict(cookie_dict, cookiejar=None, overwrite=True):
     """Returns a CookieJar from a key/value dictionary.
 
     :param cookie_dict: Dict of key/values to insert into CookieJar.
+    :param cookiejar: (optional) A cookiejar to add the cookies to.
+    :param overwrite: (optional) If False, will not replace cookies
+        already in the jar with new ones.
     """
     if cookiejar is None:
         cookiejar = RequestsCookieJar()
 
     if cookie_dict is not None:
+        names_from_jar = [cookie.name for cookie in cookiejar]
         for name in cookie_dict:
-            cookiejar.set_cookie(create_cookie(name, cookie_dict[name]))
+            if overwrite or (name not in names_from_jar):
+                cookiejar.set_cookie(create_cookie(name, cookie_dict[name]))
+
     return cookiejar
diff --git a/requests/models.py b/requests/models.py
index 48d5927d..0579b28d 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -298,7 +298,7 @@ class PreparedRequest(RequestEncodingMixin, RequestHooksMixin):
         p = PreparedRequest()
         p.method = self.method
         p.url = self.url
-        p.headers = self.headers
+        p.headers = self.headers.copy()
         p.body = self.body
         p.hooks = self.hooks
         return p
diff --git a/requests/sessions.py b/requests/sessions.py
index c136a6c8..d8e040c8 100644
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -323,6 +323,9 @@ class Session(SessionRedirectMixin):
         )
         prep = self.prepare_request(req)
 
+        # Add param cookies to session cookies
+        self.cookies = cookiejar_from_dict(cookies, cookiejar=self.cookies, overwrite=False)
+
         proxies = proxies or {}
 
         # Gather clues from the surrounding environment.
diff --git a/test_requests.py b/test_requests.py
index d1e6ed0a..3d6665ba 100755
--- a/test_requests.py
+++ b/test_requests.py
@@ -164,6 +164,12 @@ class RequestsTestCase(unittest.TestCase):
         s.get(httpbin('cookies/set?foo="bar:baz"'))
         self.assertTrue(s.cookies['foo'] == '"bar:baz"')
 
+    def test_cookie_persists_via_api(self):
+        s = requests.session()
+        r = s.get(httpbin('redirect/1'), cookies={'foo':'bar'})
+        self.assertTrue('foo' in r.request.headers['Cookie'])
+        self.assertTrue('foo' in r.history[0].request.headers['Cookie'])
+
     def test_request_cookie_overrides_session_cookie(self):
         s = requests.session()
         s.cookies['foo'] = 'bar'