The men's 400 metres hurdles event at the 2005 World Championships in Athletics was held at the Helsinki Olympic Stadium on August 6, 7 and 9.

The final was run in wet conditions following a rain story. Running in lane 2, defending champion Félix Sánchez was out with the field. Just after clearing the first hurdle, he pulled up, grabbing his right hamstring. By the third hurdle Bershawn Jackson in lane 6 had a slight lead. By the fifth, the lead had evaporated and James Carter in lane 3 had edged ahead. As Jackson continued to fade back, Dai Tamesue, to his outside in lane 7 began to separate. Tamesue assumed the lead through the final turn, entering the final straight with almost 2 metres on the Americans. Jackson put on a burst of speed, catching Tamesue over the ninth hurdle and never looking back. Deflated Tamesue was trying to hold on as Jackson and then Carter pulled away. Jackson's burst put him in first place to stay, beating Carter with a lean by over a meter. Sensing Kerron Clement gaining across the track in lane 1, Tamesue began leaning for the finish 5 metres out, falling across the finish line ahead of Clement for bronze.

All times shown are in seconds.
Q denotes qualification by place.
q denotes qualification by time.
DNS denotes did not start.
DNF denotes did not finish.
AR denotes area record
NR denotes national record.
PB denotes personal best.
SB denotes season's best.

• IAAF results