Yes, as long as it's within a certain size. You cannot bring any bag, backpack suitcase or container larger that 40cm x 35cm x 15cm into the Vatican Museums. In fact, size limits apply to all items; because of the sheer number of people that visit the Museums, space is at a premium. You can’t enter with medium to large umbrellas, any umbrellas with spiked tips, camera tripods, signage (apart from signs used by certified guides) or walking sticks – except those required by disabled visitors.
All of these items can be left in the cloakroom, which is located at the entrance to the Museums. This means that you will need to walk 15 - 20 minutes back here after you finish your tour at St Peter's Basilica. On our afternoon tours you may need to leave the tour early to collect your bag before the cloakroom closes.