diff --git a/docs/certinstall.rst b/docs/certinstall.rst
index 5ec7b7ce9..5a8cce64f 100644
--- a/docs/certinstall.rst
+++ b/docs/certinstall.rst
@@ -175,10 +175,21 @@ no such file exists, it will be generated automatically.
 Using a client side certificate
 -------------------------------
 
-You can use a client certificate by passing the ``--client-certs DIRECTORY`` option to mitmproxy.
+You can use a client certificate by passing the ``--client-certs DIRECTORY|FILE``
+option to mitmproxy. Using a directory allows certs to be selected based on
+hostname, while using a filename allows a single specific certificate to be used for
+all SSL connections. Certificate files must be in the PEM format and should
+contain both the unencrypted private key and the certificate.
+
+Multiple certs by Hostname
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If you've specified a directory to ``--client-certs``, then the following
+behavior will be taken:
+
 If you visit example.org, mitmproxy looks for a file named ``example.org.pem`` in the specified
-directory and uses this as the client cert. The certificate file needs to be in the PEM format and
-should contain both the unencrypted private key and the certificate.
+directory and uses this as the client cert.
+
 
 
 .. _Certificate Pinning: http://security.stackexchange.com/questions/29988/what-is-certificate-pinning/
\ No newline at end of file
diff --git a/libmproxy/cmdline.py b/libmproxy/cmdline.py
index 166784867..99b76e681 100644
--- a/libmproxy/cmdline.py
+++ b/libmproxy/cmdline.py
@@ -407,7 +407,7 @@ def proxy_ssl_options(parser):
     group.add_argument(
         "--client-certs", action="store",
         type=str, dest="clientcerts", default=None,
-        help="Client certificate directory."
+        help="Client certificate file or directory."
     )
     group.add_argument(
         "--no-upstream-cert", default=False,
diff --git a/libmproxy/models/connections.py b/libmproxy/models/connections.py
index 3aa522eac..0991955d9 100644
--- a/libmproxy/models/connections.py
+++ b/libmproxy/models/connections.py
@@ -174,11 +174,14 @@ class ServerConnection(tcp.TCPClient, stateobject.StateObject):
     def establish_ssl(self, clientcerts, sni, **kwargs):
         clientcert = None
         if clientcerts:
-            path = os.path.join(
-                clientcerts,
-                self.address.host.encode("idna")) + ".pem"
-            if os.path.exists(path):
-                clientcert = path
+            if os.path.isfile(clientcerts):
+                clientcert = clientcerts
+            else:
+                path = os.path.join(
+                    clientcerts,
+                    self.address.host.encode("idna")) + ".pem"
+                if os.path.exists(path):
+                    clientcert = path
 
         self.convert_to_ssl(cert=clientcert, sni=sni, **kwargs)
         self.sni = sni
diff --git a/libmproxy/proxy/config.py b/libmproxy/proxy/config.py
index c7b513112..f06e55cab 100644
--- a/libmproxy/proxy/config.py
+++ b/libmproxy/proxy/config.py
@@ -133,10 +133,12 @@ def process_proxy_options(parser, options):
 
     if options.clientcerts:
         options.clientcerts = os.path.expanduser(options.clientcerts)
-        if not os.path.exists(options.clientcerts) or not os.path.isdir(options.clientcerts):
+        if not (os.path.exists(options.clientcerts) or
+                os.path.isdir(options.clientcerts) or
+                os.path.isfile(options.clientcerts)):
             return parser.error(
-                "Client certificate directory does not exist or is not a directory: %s" %
-                options.clientcerts
+                "Client certificate argument is not a file or directory, "
+                "or does not exist: %s" % options.clientcerts
             )
 
     if options.auth_nonanonymous or options.auth_singleuser or options.auth_htpasswd:
diff --git a/test/test_proxy.py b/test/test_proxy.py
index b3e7258a1..a0530c79d 100644
--- a/test/test_proxy.py
+++ b/test/test_proxy.py
@@ -1,3 +1,4 @@
+import os
 import mock
 from OpenSSL import SSL
 
@@ -99,8 +100,11 @@ class TestProcessProxyOptions:
     def test_client_certs(self):
         with tutils.tmpdir() as cadir:
             self.assert_noerr("--client-certs", cadir)
+            self.assert_noerr(
+                "--client-certs",
+                os.path.join(tutils.test_data.path("data/clientcert"), "client.pem"))
             self.assert_err(
-                "directory does not exist",
+                "not a file or directory",
                 "--client-certs",
                 "nonexistent")
 
diff --git a/test/test_server.py b/test/test_server.py
index e48e46fe9..09cfa3815 100644
--- a/test/test_server.py
+++ b/test/test_server.py
@@ -1,3 +1,4 @@
+import os
 import socket
 import time
 from OpenSSL import SSL
@@ -316,6 +317,14 @@ class TestHTTPS(tservers.HTTPProxTest, CommonMixin, TcpMixin):
     clientcerts = True
 
     def test_clientcert(self):
+        self.config.clientcerts = os.path.join(
+            tutils.test_data.path("data/clientcert"), "client.pem")
+        f = self.pathod("304")
+        assert f.status_code == 304
+        assert self.server.last_log()["request"]["clientcert"]["keyinfo"]
+
+    def test_clientcerts(self):
+        self.config.clientcerts = tutils.test_data.path("data/clientcert")
         f = self.pathod("304")
         assert f.status_code == 304
         assert self.server.last_log()["request"]["clientcert"]["keyinfo"]