Abstract: A pet bag includes an upper bag portion and a lower bag portion, which are connectable to or separable from each other. The upper bag portion has two opposite side surfaces to which openable side panels are attached and front and rear surfaces which form openings to which scrollable screens and cover panels are attached. The lower bag portion has a bottom to which casters are mounted and opposite side surfaces to which an extendable towing bar assembly is attached. A mat is set inside the lower bag portion. As such, the pet bag may receive and hold a pet therein and the pet bag can be hand or shoulder carried or trolleyed. The upper and lower bag portions can be separated to individually serve as a pet house. When not in use, the upper bag portion can be collapsed and stored in the lower bag portion.