In athletics, Vietnam was represented by Nguyễn Thành Ngưng and Nguyễn Thị Huyền. Ngưng was chosen based on his record-breaking result at the Asian Race Walking Championships in March 2016, while Huyền's winning performance in June 2015 at the Southeast Asian Games met the criteria for both the 2015 World Championships and 2016 Summer Olympics. Ngưng and Huyền both made their Olympic debuts and were the only qualified athletes from Southeast Asia by the International Association of Athletics Federations. Ngưng participated on 12 August in the Men's 20 km walk event, finishing 60th out of 63rd competitors on a route along Pontal and failing to advance to the quarterfinals. The following day, Huyền took part in the Women's 400 m event at the Estádio Olímpico Nilton Santos, where she finished in sixth with 52.97 seconds. On 15 August, she ran her heats in 57.87 seconds and finished at the penultimate position in the Women's 400 m hurdles event, only ahead of Natalya Asanova from Uzbekistan.