A chair headrest including a headrest, a pivot member and a fastener assembly is revealed. The headrest is disposed with a damper and a guide and stop member for improving vertical movement stability and safety during adjustment. The pivot member having pivotally connected first and second portions is arranged between the headrest and a seat back. The first portion includes a pivot part with two separate ends while the second portion has a mounting part with two apart ends. The pivot part fitted to the mounting part can be rotated around an actuation axis. The fastener assembly is set between two ends of the second portion and having a connection portion for connecting the two ends of the pivot part and the two ends of the mounting part and an actuator assembly for making the two ends of the mounting part apart to be in a pressed state.