The present invention provides a tilting control assembly for a chair. The chair comprises a support device, a seat supported above the support device, and a seat back arranged behind the seat to tilt rearwardly. The tilting control assembly comprises a tilting control spring device for elastically supporting the seat back against rearward tilting thereof via a load applying member, a displacing mechanism responsive to a downward load applied to the seat for causing the load applying member to move relative to the spring device, and a lock device for preventing the load applying member from moving reversely relative to the spring device when the seat back is rearwardly tilted.