Yes, you can absolutely wear a hydration pack (like a CamelBak) at both Walt Disney World and Disneyland. Disney’s security and bag-check policies allow most backpacks, including hydration packs, provided they do not exceed 24" long x 15" wide x 18" high. You will need to remove the pack during the security screening process so the bladder and pockets can be inspected. A major "pro-tip" for 2026 is that you can refill your pack for free throughout the day at the numerous bottle-filling stations and water fountains located near restrooms, or by asking for a free cup of ice water at any "Quick Service" dining location. Some high-intensity rides with strict "no loose items" policies (like TRON Lightcycle / Run or VelociCoaster) will require you to store the pack in a locker, but for the vast majority of attractions, you can wear it or tuck it into the floor pouch of your ride vehicle. It is one of the most efficient ways to stay hydrated in the intense Florida or California heat without carrying multiple plastic bottles.