Riahi won the gold medal in pole vault at the 1996 African Championships. In decathlon he won gold medals at the 1996 African Championships, the 1999 All-Africa Games and 2004 African Championships, the silver medals at the 1995 All-Africa Games and the 2002 African Championships, and a bronze medal at the 1997 Jeux de la Francophonie. He also won the decathlon at the 1997 and 1999 Pan Arab Games. He became Tunisian champion in different events six times, and two in the decathlon.