Johnson began his athletics career as a decathlete. His best disciplines were high jump and long jump. He later specialized in the 110 meter hurdles . From the mid-1990s, he was the world's best hurdle sprinter . He won the world title at the World Athletics Championships in Gothenburg in 1995 and was Olympic champion at the Olympic Games in Atlanta a year later . He also won gold at the 1997 World Championships in Athens , 1999 in Seville and 2003 in Paris . At the 2000 Olympic Games in Sydney he was plagued by injuries, but fought his way through to the final, where he had no chance of a medal. He was also unlucky at the 2004 Olympic Games in Athens , where he stepped into a hurdle and fell in the second qualifying round. His personal best is 12.92 s. He competed in eleven races with a time under 13 seconds, more than any other hurdler in history. At the World Championships in Helsinki in 2005 , he went to win his fifth world title, which he did not succeed. The 34-year-old won the bronze medal. The French Ladji Doucouré became world champion .
In July 2010, he announced that he was ending his athletic career.
Allen Johnson is 1.78 m tall and weighed 70 kg at competition times.