Discouraged by two consecutive losses, Mugabi gained weight and did not fight for nearly fourteen months. In January 1988, he came back to fight Bryan Grant on the undercard of Mike Tyson's title defence against Larry Holmes. Mugabi won by quick knockout and set off on another knockout winning streak. He became number one contender for the WBC 154  lb title in August 1988 but could not land a fight with then-champion Donald Curry. After Curry lost his title in an upset in early 1989, Mugabi was given another opportunity to become world champion by the WBC. On July 8 of that year, Mugabi finally made his dream come true, knocking out Curry's successor Rene Jacquot in round one in Grenoble to become the WBC light middleweight champion. After two first-round knockout wins against Ricky Stackhouse and Carlos Antunes, Mugabi, who by this time was having difficulty making the weight limit of 154  lbs, put his title on the line against Terry Norris. When Norris downed the champion for the count with a right to the jaw, Mugabi received the dubious distinction as the second fighter, after Al Singer, to both win and lose a world title by the first-round knockout when he was defeated by Norris. Showing resilience, Mugabi resurfaced with two more wins and once again found himself fighting for a world title, facing Gerald McClellan on November 20, 1991, in London for the vacant WBO middleweight championship. Mugabi looked a shadow of his former self by this time, and once again came out on the losing end, again by a first-round knockout.