A lockout system for preventing a push-pull circuit breaker from being depressed while personnel work on de-energized electrical equipment. The lockout system includes an attachment member having a generally C-shaped collar defining a cylindrical recess integrated with a retainer member. The C-shaped collar is configured to resiliently expand in order to be positioned over and receive a cylindrical portion of an extended circuit breaker knob such that engagement of the circuit breaker is prevented. The retainer member includes a first channel member and a second channel member, each with a channel connected by a crossover channel that forms a continuous channel configured to receive a wire cable. Once inserted, the wire cable is firmly held in place by a locking chamber attached at each end of the wire cable, and thereafter, the lockout device can only be removed by a cutting the wire cable with a wire cutting tool.