A chair assembly includes a supporting frame disposed above a base and including a first guiding groove. A seat is pivotably connected to a backrest. Lower and front guiding wheels are mounted to rear and front ends of the seat, respectively. At least one operating board includes rear and front ends respectively having second and third guiding grooves. The lower guiding wheel is movably received in the first and second guiding grooves. The front guiding wheel is movably received in the third guiding groove. A first operating rod is pivotably connected between the supporting frame and the seat. When the operating rod retracts, the lower guiding wheel is located in rear ends of the first and second guiding grooves, and the front guiding wheel is located in a rear end of the third guiding groove. The seat moves downwards and rearwards, and the front end of the seat inclines upwards.