Doucouré finished fourth in the 60 m hurdles final at the
2003 World Indoor Championships. He was eliminated in the 110m hurdles semi-finals of the
2003 World Championships, his debut appearance in a
World Championships. Doucouré competed in only one event – the
110 m hurdles – at the
2004 Olympics, his first Olympic Games. He had the fastest time among all the competitors in each of the first two rounds and in the semi-finals. But he finished eighth and last in the final in a time of 13.76 s; he was actually in second place before clipping the last hurdle.
Doucouré won the 60 m hurdles gold medal at the
2005 European Indoor Championships, his first European Championships, Olympic Games or World Championships medal at the senior level. At the French Athletics Outdoor Championships held in
Angers on 15 July 2005, Doucouré won the 110m hurdles for the second consecutive year in a time of 12.97 s, setting a new
national outdoor record and becoming he first French athlete to go under 13 seconds in that event. It was the world's best performance that year. At the
2005 World Championships, Doucouré won the 110m hurdles gold medal in a time of 13:07 s, beating 2004 Olympic Champion
Liu Xiang by one hundredth of a second and veteran
Allen Johnson by three hundredths of a second. He (together with
Ronald Pognon,
Eddy De Lépine and
Lueyi Dovy) also won the gold medal in the
4×100 metres relay event at the same championships. He was named the 2005
L'Équipe Champion of Champions (France category) for his outstanding performance on the track that year.