She began her career on television with guest-starring roles. In 2007, she had a supporting role in the film The Hitcher. She later returned to television and had a number of guest and recurring roles on dramatic series. She played Mariella Moretta in the TNT crime drama, Southland from 2009 to 2011, and Theresa Lopez on the ABC Family drama, The Lying Game (2012–2013). She also had recurring roles on Vanished, The Unit, Breakout Kings, and Nashville.
Martinez was a regular cast member on the short-lived primetime soap opera, Hollywood Heights in 2012. In 2013 she began starring in the Amazon comedy series, Alpha House. In 2014, Martinez also was cast as recurring in The CW comedy-drama Jane the Virgin, and HBO crime drama True Detective.
Martinez portrays Ms. Lint in the Amazon series, The Tick.