Wong was born in the Scarborough district of Toronto, Ontario, to parents of Cambodian descent. Wong began acting in community theatre while attending L'Amoreaux Collegiate Institute and worked in a variety of TV production jobs starting at the age of 14. She later studied radio and television arts at Ryerson University. Wong continued acting while at Ryerson and in 2005, she landed a role in the TV series This Is Wonderland followed by Runaway the next year. She also studies taekwondo but had to stop sparring competitively due to her acting schedule. Wong's martial arts background helped her land the role of Knives Chau in Scott Pilgrim vs. the World in October 2009. She auditioned for the part three times. On her second audition director Edgar Wright was surprised to find out that she had a green belt in taekwondo and was intrigued by this "sweetfaced young lady being a secret badass". Wong expressed that the role of Knives Chau caught her eye because "it's not every day that as an Asian female, [you get] to be able to read a role that's empowering, that has a great arc, and that's so integral to the story as a whole." Before Scott Pilgrim vs. the World, Wong also appeared in the TV show, Unnatural History.
In 2011, Wong had a recurring role as Nurse Suzy Chao in the Global/ABC series Combat Hospital. In January 2012, she was nominated for an ACTRA Award for Outstanding Performance by a Female for her work portraying an illegal immigrant smuggled across the ocean in a shipping container in the short film Silent Cargo. In February 2012, Wong landed a role in the Sex and the City prequel series, The Carrie Diaries, playing Jill "Mouse" Thompson, Carrie’s best friend from high school who is described as pragmatic, bright and super loyal. In April 2012, it was reported that she had joined the cast of Silent Night, a loose remake of the 1984 horror film Silent Night, Deadly Night.