diff --git a/aiven/client/cli.py b/aiven/client/cli.py
index db096f8a..5f2c0627 100644
--- a/aiven/client/cli.py
+++ b/aiven/client/cli.py
@@ -1558,7 +1558,7 @@ def service__metrics(self):
     @arg.service_name
     @arg("--pool-name", help="Connection pool name", required=True)
     @arg("--dbname", help="Service database name", required=True)
-    @arg("--username", help="Service username", required=True)
+    @arg("--username", help="Service username")
     @arg("--pool-size", type=int, help="Connection pool size")
     @arg("--pool-mode", help="Connection pool mode")
     @arg.json
@@ -1578,22 +1578,26 @@ def service__connection_pool_create(self):
     @arg.service_name
     @arg("--pool-name", help="Connection pool name", required=True)
     @arg("--dbname", help="Service database name")
-    @arg("--username", help="Service username")
+    @arg("--username", help="Service username (set to empty string to remove the pool username)")
     @arg("--pool-size", type=int, help="Connection pool size")
     @arg("--pool-mode", help="Connection pool mode")
     @arg.json
     def service__connection_pool_update(self):
         """Update a connection pool for a given PostgreSQL service"""
-        self.client.update_service_connection_pool(
+        kwargs = dict(
             project=self.get_project(),
             service=self.args.service_name,
             pool_name=self.args.pool_name,
             dbname=self.args.dbname,
-            username=self.args.username,
             pool_size=self.args.pool_size,
             pool_mode=self.args.pool_mode,
         )
 
+        if self.args.username is not None:
+            kwargs["username"] = self.args.username if self.args.username != "" else None
+
+        self.client.update_service_connection_pool(**kwargs)
+
     @arg.project
     @arg.service_name
     @arg("--pool-name", help="Connection pool name", required=True)
diff --git a/aiven/client/client.py b/aiven/client/client.py
index cd1b1fe0..fa72ec13 100644
--- a/aiven/client/client.py
+++ b/aiven/client/client.py
@@ -18,6 +18,8 @@
 except ImportError:
     __version__ = "UNKNOWN"
 
+UNCHANGED = object()  # used as a sentinel value
+
 
 class Error(Exception):
     """Request error"""
@@ -221,11 +223,13 @@ def create_service_connection_pool(
         service,
         pool_name,
         dbname,
-        username,
+        username=None,
         pool_size=None,
         pool_mode=None,
     ):
-        body = {"database": dbname, "username": username, "pool_name": pool_name}
+        body = {"database": dbname, "pool_name": pool_name}
+        if username:
+            body["username"] = username
         if pool_size:
             body["pool_size"] = pool_size
         if pool_mode:
@@ -242,12 +246,12 @@ def update_service_connection_pool(
         service,
         pool_name,
         dbname=None,
-        username=None,
+        username=UNCHANGED,
         pool_size=None,
         pool_mode=None,
     ):
         body = {}
-        if username is not None:
+        if username is not UNCHANGED:
             body["username"] = username
         if dbname is not None:
             body["database"] = dbname
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 5eb5ccf1..42edfea8 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -203,3 +203,95 @@ def test_version_eol_check():
     with mock.patch("aiven.client.cli.get_current_date", return_value=fake_time_soon):
         cli._do_version_eol_check(service_type, service_version)  # pylint: disable=protected-access
         cli.confirm.assert_called()  # Confirmation should have been asked
+
+
+def test_create_service_connection_pool():
+    aiven_client = mock.Mock(spec_set=AivenClient)
+    aiven_client.update_service_connection_pool.return_value = {"message": "created"}
+
+    build_aiven_cli(aiven_client).run(
+        args=[
+            "service", "connection-pool-create", "--project", "testproject", "--dbname", "defaultdb", "--pool-name", "foo",
+            "--pool-size=23", "--username", "avnadmin", "pg-foo-bar"
+        ]
+    )
+
+    aiven_client.create_service_connection_pool.assert_called_with(
+        project="testproject",
+        service="pg-foo-bar",
+        pool_name="foo",
+        dbname="defaultdb",
+        username="avnadmin",
+        pool_size=23,
+        pool_mode=None
+    )
+
+    build_aiven_cli(aiven_client).run(
+        args=[
+            "service", "connection-pool-create", "--project", "testproject", "--dbname", "defaultdb", "--pool-name", "bar",
+            "pg-foo-bar"
+        ]
+    )
+
+    aiven_client.create_service_connection_pool.assert_called_with(
+        project="testproject",
+        service="pg-foo-bar",
+        pool_name="bar",
+        dbname="defaultdb",
+        username=None,
+        pool_size=None,
+        pool_mode=None
+    )
+
+
+def test_update_service_connection_pool():
+    aiven_client = mock.Mock(spec_set=AivenClient)
+    aiven_client.update_service_connection_pool.return_value = {"message": "updated"}
+
+    # pin
+    build_aiven_cli(aiven_client).run(
+        args=[
+            "service", "connection-pool-update", "--project", "testproject", "--pool-name", "foo", "--username", "avnadmin",
+            "pg-foo-bar"
+        ]
+    )
+
+    aiven_client.update_service_connection_pool.assert_called_with(
+        project="testproject",
+        service="pg-foo-bar",
+        pool_name="foo",
+        dbname=None,
+        username="avnadmin",
+        pool_size=None,
+        pool_mode=None
+    )
+
+    # unpin
+    build_aiven_cli(aiven_client).run(
+        args=[
+            "service", "connection-pool-update", "--project", "testproject", "--pool-name", "foo", "--username", "",
+            "pg-foo-bar"
+        ]
+    )
+
+    aiven_client.update_service_connection_pool.assert_called_with(
+        project="testproject",
+        service="pg-foo-bar",
+        pool_name="foo",
+        dbname=None,
+        username=None,
+        pool_size=None,
+        pool_mode=None
+    )
+
+    # leave username as is, change pool-size instead
+    build_aiven_cli(aiven_client).run(
+        args=[
+            "service", "connection-pool-update", "--project", "testproject", "--pool-name", "foo", "--pool-size", "42",
+            "pg-foo-bar"
+        ]
+    )
+
+    aiven_client.update_service_connection_pool.assert_called_with(
+        project="testproject", service="pg-foo-bar", pool_name="foo", dbname=None, pool_size=42, pool_mode=None
+    )