An exemplary modular hold-open device is configured for use with a door closer comprising a body, a pinion rotatably mounted to the body, and an armature connected with the pinion. The modular hold-open device is configured to be mounted to the door closer, to selectively prevent rotation of the pinion by exerting on the pinion a resistive torque in a door-opening direction, and to cease exerting the resistive torque in response to a door-closing torque on the pinion exceeding a threshold torque to thereby permit rotation of the pinion in the door-closing direction.