A combination clutch and brake for rotary power mowers of the type wherein the blade is fixed to a spindle driven by the engine through an endless belt type drive transmission. A medially pivoted lever has an idler roll at one end to engage and tension the belt and thereby activate the drive transmission when the lever is rocked in one direction and a claw at its other end which, upon movement of the lever in the opposite direction, engages the notched periphery of a brake disc encircling the blade spindle and frictionally engaged with a companion disc that is fixed with respect to the spindle. The lever is spring-biased in the direction to engage the brake disc and thereby stop blade rotation concomitantly with deactivation the drive transmission whenever a deadman control on the mower handle is released.