diff --git a/django/db/backends/dummy/base.py b/django/db/backends/dummy/base.py
index 36c6480a78..0e2edc73cf 100644
--- a/django/db/backends/dummy/base.py
+++ b/django/db/backends/dummy/base.py
@@ -39,6 +39,7 @@ class DatabaseClient(BaseDatabaseClient):
 class DatabaseCreation(BaseDatabaseCreation):
     create_test_db = ignore
     destroy_test_db = ignore
+    serialize_db_to_string = ignore
 
 
 class DatabaseIntrospection(BaseDatabaseIntrospection):
diff --git a/django/test/utils.py b/django/test/utils.py
index ddb85127dc..a3594bfb6d 100644
--- a/django/test/utils.py
+++ b/django/test/utils.py
@@ -189,6 +189,7 @@ def setup_databases(
     test_databases, mirrored_aliases = get_unique_databases_and_mirrors(aliases)
 
     old_names = []
+    serialize_connections = []
 
     for db_name, aliases in test_databases.values():
         first_alias = None
@@ -200,15 +201,14 @@ def setup_databases(
             if first_alias is None:
                 first_alias = alias
                 with time_keeper.timed("  Creating '%s'" % alias):
-                    serialize_alias = (
-                        serialized_aliases is None or alias in serialized_aliases
-                    )
                     connection.creation.create_test_db(
                         verbosity=verbosity,
                         autoclobber=not interactive,
                         keepdb=keepdb,
-                        serialize=serialize_alias,
+                        serialize=False,
                     )
+                    if serialized_aliases is None or alias in serialized_aliases:
+                        serialize_connections.append(connection)
                 if parallel > 1:
                     for index in range(parallel):
                         with time_keeper.timed("  Cloning '%s'" % alias):
@@ -229,6 +229,16 @@ def setup_databases(
             connections[mirror_alias].settings_dict
         )
 
+    # Serialize content of test databases only once all of them are setup
+    # to account for database mirroring and routing during serialization.
+    # This slightly horrific process is so people who are testing on databases
+    # without transactions or using TransactionTestCase still get a clean
+    # database on every test run.
+    for serialize_connection in serialize_connections:
+        serialize_connection._test_serialized_contents = (
+            serialize_connection.creation.serialize_db_to_string()
+        )
+
     if debug_sql:
         for alias in connections:
             connections[alias].force_debug_cursor = True
diff --git a/tests/test_runner/tests.py b/tests/test_runner/tests.py
index fba8dd3b6f..d58d47b96b 100644
--- a/tests/test_runner/tests.py
+++ b/tests/test_runner/tests.py
@@ -938,14 +938,17 @@ class SetupDatabasesTests(unittest.TestCase):
                 },
             }
         )
-        with mock.patch(
-            "django.db.backends.dummy.base.DatabaseWrapper.creation_class"
-        ) as mocked_db_creation:
-            with mock.patch("django.test.utils.connections", new=tested_connections):
-                self.runner_instance.setup_databases()
+        with (
+            mock.patch(
+                "django.db.backends.dummy.base.DatabaseWrapper.creation_class"
+            ) as mocked_db_creation,
+            mock.patch("django.test.utils.connections", new=tested_connections),
+        ):
+            self.runner_instance.setup_databases()
         mocked_db_creation.return_value.create_test_db.assert_called_once_with(
-            verbosity=0, autoclobber=False, serialize=True, keepdb=False
+            verbosity=0, autoclobber=False, serialize=False, keepdb=False
         )
+        mocked_db_creation.return_value.serialize_db_to_string.assert_called_once_with()
 
 
 @skipUnlessDBFeature("supports_sequence_reset")