Banks is known for her roles in Seabiscuit, Heights, the Spider-Man films (playing the part of Betty Brant), and the cult comedy Wet Hot American Summer. She quickly gained widespread exposure through movies like The 40-Year-Old Virgin and Slither. She also plays Mark Wahlberg's love interest in the Disney movie, Invincible.

In May 2006, she appeared in the season five finale of the NBC comedy-drama Scrubs as Dr. Kim Briggs, the love interest of J.D. (Zach Braff). The character has appeared throughout season six and seven as a recurring guest star.

In 2005, she also appeared on the show Stella, as she is a long time friend of its creators/stars, the Stella comedy troupe. In 2007, Banks played the female lead in the comedy Meet Bill, alongside Aaron Eckhart and Jessica Alba. Banks also has a small role in the 2007 family comedy Fred Claus, along with Vince Vaughn and Paul Giamatti, and played a love interest in the 2008 comedy Definitely, Maybe.

Banks stars with Set