A brake wear indicator for an air brake system that includes an actuator having a diaphragm adapted to move within the actuator in response to air pressure, and a push rod mechanically coupled to the diaphragm and extending from the actuator through an opening in the actuator wall. The brake wear indicator comprises marking means having a generally cylindrical outer surface, a longitudinal axis, a distance indicator on the outer surface, and means for securing the marking means to the push rod within the opening. The marking means thereby provides a visual indication of the position of the push rod along such axis at the opening. In a preferred embodiment, the marking means comprises a tubular member having an internal diameter large enough to accommodate the push rod, and an outside diameter small enough to permit the tubular member to move through the opening, and a flange having an outside diameter too large to fit through the opening. An indicator formed integrally with the push rod is also disclosed.