A toner monitoring network printer system and method of monitoring a toner cartridge thereof. A first network printer includes a communication module to communicate data with terminals through a network and to support communication with a second network printer, a toner residue computing part to compute a toner residue value of a toner cartridge based on a number of pages printed by the first network printer, a memory to store toner cartridge information including the toner residue value computed by the toner residue computing part, and a central processing device to control the communication module to provide the second network printer with the toner cartridge information including the toner residue value computed by the toner residue computing part, and to control the toner cartridge information including the toner residue value provided from a second network printer to be stored in at least one of the memory and the toner cartridge.