[2] The event was won by Félix Sánchez of the Dominican Republic, the second victory in the men's long hurdles for both the man and the nation.

However, when the Olympics returned in 1920 after World War I, the men's 400 metres hurdles was back and would continue to be contested at every Games thereafter.

Four of the eight finalists from the 2008 Games returned: gold medalist (and 2000 winner) Angelo Taylor of the United States, silver medalist Kerron Clement of the United States, fifth-place finisher L. J. van Zyl of South Africa, and eighth-place finisher Periklis Iakovakis of Greece.

Also returning was the 2004 gold medalist Félix Sánchez of the Dominican Republic, who had not advanced out of the quarterfinals in Beijing 2008.

[2] Comoros, Estonia, Serbia, Togo, Trinidad and Tobago, and Uruguay each made their debut in the event.

The slowest time qualifier was Kenneth Medwood in 49.78, though Stanislav Melnykov managed to get into the semis automatically with a 50.13 in the slow fifth heat.

Less than a month before his 35th birthday, Félix Sánchez, the 2001 and 2003 World Champion showed he was still in the game, running a season best 47.76.

The second semi was dominated by world leader Javier Culson and defending champion Angelo Taylor.

In the third semi, American trials champion Michael Tinsley and Leford Green separated from the rest of the field.

In repeating as Olympic champion non-consecutively, Sánchez joined a rare club including Paavo Nurmi, Volodymyr Holubnychy, Heike Drechsler, Nina Romashkova, Edwin Moses (caused by the boycott) and Angelo Taylor.