An improved motor vehicle brake-pedal locking device (10) that mechanically maintains the vehicle brake-pedal (60) in a depressed position to prevent the vehicle from being driven. The device includes a horizontally and vertically pivoting brake-pedal swing-arm interfacing structure (12) that is disclosed in two designs. Both designs include a channel (12A),(38C) that engages the brake-pedal swing-arm (62). To the back end (18B),(34B) of the structure (12) is attached the back end (50B of a locking tube (50). Inserted into this locking tube (50), is a locking rod (52) having attached to its back end (52B) a forked section (56A) that attaches to a vehicle seat (64). The device is installed by placing the structure (12) over the swing-arm (62) and the forked section (56A) secured to the seat (64). The device (10) is then depressed to place the brake-pedal (60) in a depressed position in which position the device is locked in place.