Vien started her first swimming lessons when she was five and quickly progressed. At 15, she won 10 gold medals at the national swimming championship for different ages. Vien participated in her first SEA Games in 2011 and claimed two silvers. A year later, a 16-year-old Vien competed in her first Olympics.
At SEA Games 2013, Vien started to shine, winning three gold, two silver, and one bronze medal while breaking two records of the event. After 54 years, a female swimmer from Vietnam finally became a gold medalist.