Abstract: A chair arm adjustment mechanism is disclosed. The mechanism includes a T-shaped driving member, a spring biased trigger member in a vertical section of the driving member and having a finger tab, a lock members including two bifurcated ends; a positioning member fitted around a portion of the driving member and including a longitudinal channel, and an upper and lower shrouds. Lifting the finger tab will pivot the bifurcated ends of the lock members toward each other until a joining portion thereof is stopped. Releasing the finger tab will lower the trigger member, pivot the bifurcated ends away each other until the joining portion thereof is stopped.