Lawson began acting at the age of nine, having appeared in commercials for Barbie and Revlon. In 1993, she was cast in the television series Saved by the Bell: The New Class as series regular Megan Jones. She appeared in multiple episodes of The WB sitcoms Sister, Sister as Rhonda Coley and The Steve Harvey Show as Rosalind. In 1996, she co-starred in the UPN sitcom Goode Behavior—which lasted for just one season—as Bianca Goode, the teenage daughter of the titular family. In 1997, she appeared in Buffy the Vampire Slayer as vampire slayer Kendra Young. In 1999, she appeared in The WB's Dawson's Creek as rival character Nikki Green.
In 2009, Lawson was cast as Shawna in The Secret Life of the American Teenager. That same year, she was cast in the CW television series The Vampire Diaries, as witch Emily Bennett. In December 2009, she was cast as Maya St. Germain in the ABC Family series Pretty Little Liars, based on the book series by Sara Shepard.[6] She appeared in that show from June 2010 through August 2012. Since 2012, she has had a recurring role as Ms. Morell in the MTV television series Teen Wolf, based on the original film from 1985. In 2014, Lawson had a recurring role as Eva in Witches of East End. In 2015, she was cast as series regular Talia Freeman in season three of Rogue.