diff --git a/vc_zoom/indico_vc_zoom/plugin.py b/vc_zoom/indico_vc_zoom/plugin.py
index 10152089..04745077 100644
--- a/vc_zoom/indico_vc_zoom/plugin.py
+++ b/vc_zoom/indico_vc_zoom/plugin.py
@@ -895,6 +895,16 @@ def _get_registrant_email(self, registration):
                 return enterprise_email.lower()
         return registration.email
 
+    def _get_zoom_host_emails(self, vc_room):
+        # Zoom rejects registering the meeting host or any pre-assigned alt host (API error 3027).
+        identifiers = [vc_room.data['host'], *(vc_room.data.get('alternative_hosts') or [])]
+        emails = set()
+        for ident in identifiers:
+            principal = principal_from_identifier(ident, require_user_token=False)
+            if principal and (email := find_enterprise_email(principal)):
+                emails.add(email.lower())
+        return emails
+
     def _get_user_registration(self, event, user):
         return (Registration.query.with_parent(event)
                 .join(Registration.registration_form)
@@ -1003,7 +1013,8 @@ def _collect_room_ops(self, pending):
                 else:
                     room_ops[zoom_id]['remove'][email] = registration.id
         for ops in room_ops.values():
-            ops['add'] = list(ops['add'].values())
+            skip = self._get_zoom_host_emails(ops['vc_room'])
+            ops['add'] = [e for e in ops['add'].values() if e['data']['email'].lower() not in skip]
         return room_ops
 
     def _has_other_active_room_registration(self, vc_room, email, exclude_ids):
diff --git a/vc_zoom/tests/registration_test.py b/vc_zoom/tests/registration_test.py
index 8c8595f0..a87104d0 100644
--- a/vc_zoom/tests/registration_test.py
+++ b/vc_zoom/tests/registration_test.py
@@ -728,3 +728,29 @@ def test_registration_summary_hides_zoom_link_if_not_registered_in_zoom(
     html = zoom_plugin._render_registration_zoom_link(registration, from_management=False)
 
     assert html == ''
+
+
+@pytest.mark.usefixtures('smtp')
+def test_batch_excludes_host_and_alt_host(db, zoom_plugin, zoom_api_registrants, reg_form, zoom_user, create_user):
+    """When the queue mixes host, alt host, and regular participants, only the regular ones reach Zoom."""
+    alt_host = create_user(2, email='alt.host@megacorp.xyz')
+    event = reg_form.event
+    _make_complete_registration(db, zoom_plugin, reg_form, zoom_user.email, 'Don', 'Orange')
+    _make_complete_registration(db, zoom_plugin, reg_form, alt_host.email, 'Alt', 'Host')
+    _make_complete_registration(db, zoom_plugin, reg_form, 'alice@example.com', 'Alice', 'Smith')
+    _make_complete_registration(db, zoom_plugin, reg_form, 'bob@example.com', 'Bob', 'Jones')
+
+    zoom_plugin.settings.set('allow_auto_register', True)
+    zoom_api_registrants['add_meeting_registrant'].reset_mock()
+    zoom_api_registrants['batch_meeting_registrants'].reset_mock()
+
+    vc_room, assoc = _create_vc_room_with_assoc(db, event, zoom_user)
+    vc_room.data['alternative_hosts'] = [alt_host.persistent_identifier]
+    signals.vc.vc_room_created.send(vc_room, event=event, assoc=assoc)
+    zoom_plugin._flush_pending_registrations(None)
+
+    zoom_api_registrants['add_meeting_registrant'].assert_not_called()
+    assert zoom_api_registrants['batch_meeting_registrants'].call_count == 1
+    batch_data = zoom_api_registrants['batch_meeting_registrants'].call_args[0][1]
+    batch_emails = {r['email'] for r in batch_data['registrants']}
+    assert batch_emails == {'alice@example.com', 'bob@example.com'}