In the 2012 London Olympic Games, Nguyen won two Olympic silver medals after competing in the Men's artistic team all-around, individual all-around, floor and parallel bars. Nguyen collected the first all-around gymnastics medal for Germany since the 1936 Summer Olympic Games held in Berlin. His second silver medal was on the individual apparatus final of parallel bars, and the German team all-around finished in 7th place. Lastly, he finished in 8th place on the floor individual apparatus final, an event, for which he had little time to prepare and initially not qualified but was brought as first reserve last minute to complete the roster of the event final, after another athlete who had qualified for the final withdrew due to injury. At the European Championships in 2014, he placed 4th on the team, but failed to qualify for any of the individual finals. In September 2014, he was at the home championships in Stuttgart on parallel bars and rings which is where he tore his ACL.