The men's 400 metre individual medley (IM) at the 2007 World Aquatics Championships took place on 1 April (heats and final) at the Rod Laver Arena in Melbourne, Australia. As the event was over 400 meters in length, no semifinals were held in it and the top 8 swimmers from the preliminary heats advance directly to the single final heat. 50 swimmers were entered in the event, of which 49 swam.