An adjustable armrest for a vehicle includes a molded shell and a blocking member, both rotatably mounted to a pivot pin that is attached to a vehicle such as to the seat. The shell houses a linearly operating control mechanism that allows the armrest to be adjusted to a variety of positions, yet remember an initially selected position. The blocking member has an abutment surface that is positioned to normally engage a stop pin that is fixedly mounted to the vehicle for limiting the range of rotational movement of the armrest. In the preferred embodiment, the control mechanism has a first end including an interlocking member adapted to normally interengage the blocking member, and a second end opposite the first end that may be actuated by the user to selectively release the interengagement between the blocking member and the interlocking member.