A collapsible cage for dogs or rabbits has a rectangular base, fold-down end walls folding side walls and a roof. The walls and roof are made of metal grids. The end walls fold down onto the base one over the other. The side walls fold in the middle concertina-wise and are hinged at the top to opposite edges of the roof allowing the side walls and roof to collapse onto the base over the end walls. The base has a pull-out tray or pan and an access door is provided in one of the end walls. Releasable clips are provided to hold the walls and roof together in an elevated position of the structure.