Continuing to win his fights, at the end of 1887, Kelly claimed the title of American bantam-weight champion, having defeated Tommy Russell. In early 1888, Kelly fought a draw against George Dixon and then obtained his first victory over Michael Chappie Moran, who would later become his greatest career rival.
In a second match with Moran, in an 1889 fight that was billed as a world title bantam-weight fight, Kelly was victorious, allowing him to claim the world bantam-weight title. However, only a few months later, in his third duel against Moran, Kelly was defeated and the world title went to Moran.
Nevertheless, in early 1890, Kelly and Moran fought a fourth time. Kelly managed to serve a definitive knockout to his rival during this match, as Kelly laid Moran out on the canvas within a time of 38 minutes. Kelly held on to his world bantam-weight title until 1892, when he was dethroned by Englishman Billy Plimmer in 10 rounds at Coney Island.
Finally, after a discouraging nine years of on and off fighting with just three wins to eight losses, Kelly decided to retire in 1901 after four consecutive draws against the light-weight fighter, Kid Goodman.
