An adjustable side view mirror assembly (50) which includes a conventional pivotal mounting bracket (20) having an upper generally horizontal support portion (38). An adapter block has two halves (70,72) with matching slots (76) and (74) one above the other. The lower slot (74) is mounted on support portion (38) while the upper slot receives a slide bar (90). The mirror (22) is mounted at the outer end (92) of the slide bar (90) while stop means (96) are located at the inner end (94) to prevent the bar from sliding on through. A threadable member (102) locks the slide bar in the desired position.