Born in Overland Park, Kansas,[2] Lancaster has appeared on Sabrina, the Teenage Witch, Dawson's Creek, That '70s Show, Scrubs, and CSI: Crime Scene Investigation.

Most notably, she appeared as Ellie Bartowski Woodcomb on the NBC series Chuck from 2007 to 2012.

Lancaster has also worked as a jealous girlfriend-turned-serial killer in the movie Lovers Lane, and as the blackjack dealer, Veronica Harold, on CBS's short-lived Dr. Vegas.

In 2019, Lancaster made her directorial debut with the film Josie & Jack, based on Kelly Braffet's 2005 novel of the same name.

[6] In 1997, Sarah was nominated with the rest of cast of Saved by the Bell for Best Performance in a TV Series - Young Ensemble.