Thiessen's television work includes appearing on What About Brian and in a nine-episode guest-starring role...

on Good Morning Miami. In 2003, she starred in the series Fastlane with Peter Facinelli and Bill Bellamy, directed by McG. She also guest-starred on the hit comedy Just Shoot Me in a three-episode arc, portraying a columnist who becomes romantically involved with David Spade’s character. She also appeared in a recurring role on the comedy Two Guys and a Girl.

Thiessen began modeling at the age of 8 and soon went on to star in the television series Saved by the Bell for five seasons. At the same time, she made her feature film debut in Son in Law opposite Pauly Shore. In 1993, she showed her range when producer Aaron Spelling cast her in Beverly Hills, 90210 where she portrayed the multi-layered Valerie Malone for five seasons.

Among Thiessen’s other feature film roles are the comedy Ladies Man, the independent film Speedway Junky with Jesse Bradford, Jonathan Taylor Thomas and Daryl Hannah, Love Stinks with Tyra Banks and French Stewart, and the horror/comedy spoof Shriek If You Know What I did Last Friday the Thirteenth opposite Tom Arnold. Thiessen also can be seen in the 2008 feature Weapons, which premiered at the Sundance Film Festival.

In 2005, Thiessen started up her own production company – Tit 4 Tat Productions – while directing her first short film Just Pray the same year. Just Pray went on to win many awards at top film festivals around the country.