At the 2008 Summer Olympics in Beijing, Nguyen qualified again for the second time in the 100 m breaststroke. He received a FINA wild card entry by achieving his personal best of 1:03.73 from his gold medal triumph at the 2007 Southeast Asian Games in Bangkok, Thailand. Nguyen challenged five other swimmers in heat two, including fellow two-time Olympian Sergiu Postica of Moldova. He raced to fourth place by 0.14 of a second behind Lebanon's Wael Koubrousli in 1:06.36. Nguyen failed to advance into the semifinals, as he placed fifty-eighth overall on the first night of the preliminaries.