A collapsible water filter has a telescopic container and a filter cartridge. The telescopic container has a telescopic segment and a connection segment, and the telescopic segment having a first end and a second end opposite to the first end. The telescopic segment defines a holding space, and the holding space has a first opening adjacent to the first end of the telescopic segment. When the first end and the second end of the telescopic segment are under a force such that the first end and the second end approach each other, the volume of the holding space is reduced. When the first end and the second end of the telescopic segment are under a force such that the first end and the second end move away from each other, the volume of the holding space is increased.