In 2012 she co-starred on the ABC supernatural drama series 666 Park Avenue, which was canceled midway through its season.
In Spring 2014, she debuted her role of DEA Special Agent Talia Del Campo on the CBS series NCIS: Los Angeles, which has since become a recurring role.
In August 2015, Mason debuted in her role as Ofelia Salazar, on the Walking Dead companion series, Fear the Walking Dead.
In addition to English, Mason speaks Swedish, French, Spanish, and Persian. However, on the Swedish talk show Skavlan on September 30, 2016, she declared that she no longer speaks Swedish, but she does still understand it.
Mason was born in Linköping, Sweden, and grew up in the neighborhood of Ryd, Linköping. She moved to the United States with her family at the age of 12. She was raised around the Chicago area. She currently lives in Los Angeles, California with her husband David Denman, whom she married in August 2014. The couple welcomed their first child on 10 January 2018, a son named Caius Kane Denman.