A circuit breaker lock-off device is side-mounted to a circuit breaker case in a tenacious engagement. The lock-off device has a generally planar body carrying a lock-off arm pivotable in a plane parallel to the body to place an engagement tab extending therefrom into a position for preventing movement of the breaker handle without being physically attached to the breaker handle. The lock-off arm and the body further have complementary rings for accepting a padlock shackle in the locked off position. The invention allows a rugged lock-off accessory which is field installable and which can accommodate various breaker handle geometries.