diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 6aed100..cca8edd 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -39,6 +39,10 @@ Fixes
 * **Amazon SES:** Fix bcc, which wasn't working at all on non-template sends.
   (Thanks to `@mwheels`_ for reporting the issue.)
 
+* **Mailjet:** Fix TypeError when sending to or from addresses with display names
+  containing commas (introduced in Django 2.2.15, 3.0.9, and 3.1).
+
+
 Features
 ~~~~~~~~
 
diff --git a/anymail/backends/mailjet.py b/anymail/backends/mailjet.py
index 12d57a1..62363e0 100644
--- a/anymail/backends/mailjet.py
+++ b/anymail/backends/mailjet.py
@@ -1,3 +1,5 @@
+from email.header import Header
+
 from six.moves.urllib.parse import quote
 
 from ..exceptions import AnymailRequestsAPIError
@@ -158,12 +160,16 @@ class MailjetPayload(RequestsPayload):
 
     def _format_email_for_mailjet(self, email):
         """Return EmailAddress email converted to a string that Mailjet can parse properly"""
-        # Workaround Mailjet 3.0 bug parsing display-name with commas
+        # Workaround Mailjet 3.0 bug parsing RFC-2822 quoted display-name with commas
         # (see test_comma_in_display_name in test_mailjet_backend for details)
         if "," in email.display_name:
-            return EmailAddress(email.display_name.encode('utf-8'), email.addr_spec).formataddr('utf-8')
-        else:
-            return email.address
+            # Force MIME "encoded-word" encoding on name, to hide comma from Mailjet.
+            # We just want the RFC-2047 quoting, not the header wrapping (which will
+            # be Mailjet's responsibility), so set a huge maxlinelen.
+            encoded_name = Header(email.display_name.encode('utf-8'),
+                                  charset='utf-8', maxlinelen=1000000).encode()
+            email = EmailAddress(encoded_name, email.addr_spec)
+        return email.address
 
     #
     # Payload construction
diff --git a/tests/test_mailjet_backend.py b/tests/test_mailjet_backend.py
index 749e392..d18d157 100644
--- a/tests/test_mailjet_backend.py
+++ b/tests/test_mailjet_backend.py
@@ -106,13 +106,19 @@ class MailjetBackendStandardEmailTests(MailjetBackendMockAPITestCase):
         # (This shouldn't be necessary in Mailjet 3.1, where Name becomes a separate json field for Cc/Bcc.)
         msg = mail.EmailMessage(
             'Subject', 'Message', '"Example, Inc." <from@example.com>',
-            ['"Recipient, Ltd." <to@example.com>'])
+            ['"Recipient, Ltd." <to@example.com>'],
+            cc=['"This is a very long display name, intended to test our workaround does not insert carriage returns'
+                ' or newlines into the encoded value, which would cause other problems" <long@example.com']
+        )
         msg.send()
         data = self.get_api_call_json()
         self.assertEqual(data['FromName'], 'Example, Inc.')
         self.assertEqual(data['FromEmail'], 'from@example.com')
         # self.assertEqual(data['To'], '"Recipient, Ltd." <to@example.com>')  # this doesn't work
         self.assertEqual(data['To'], '=?utf-8?q?Recipient=2C_Ltd=2E?= <to@example.com>')  # workaround
+        self.assertEqual(data['Cc'], '=?utf-8?q?This_is_a_very_long_display_name=2C_intended_to_test_our_workaround'
+                                     '_does_not_insert_carriage_returns_or_newlines_into_the_encoded_value=2C_which'
+                                     '_would_cause_other_problems?= <long@example.com>')
 
     def test_email_message(self):
         email = mail.EmailMessage(