A vertically adjustable armrest that is suitable for use in connection with various types of passenger vehicles, including commercial aircraft. The armrest includes a slide mechanism for permitting easy height adjustment of the armrest and also includes a locking mechanism for securely locking the headrest in the desired elevated position. The armrest moves in a smooth vertical motion and is continuously biased toward an upraised position. Vertical adjustment of the armrest is accomplished by pushing a push button located in the upper portion of the armrest.