Watch Kaitlin Olson Online

Born in Tigard, Oregon, Olson was the daughter of a previous publisher of The Portland Tribune. At the age of 12, she was involved in a serious bicycle accident requiring reconstructive surgery.She attended the University of Oregon majoring in theater. She later moved to Los Angeles to pursue acting professionally. Olson was a part of the famed improvisational group the Groundlings. She made several guest appearances in films and TV series such as Curb Your Enthusiasm (as Becky, Larry David's sister-in-law) and The Drew Carey Show (as Mimi Bobeck's nemesis, Traylor). Olson toured with the USO to Bosnia, Kosovo and Norway. Olson has appeared on The Jamie Kennedy Experiment, Out of Practice, Miss Match and Punk'd. She had a minor role in the film Coyote Ugly.

In 2005, she was cast as Deandra Reynolds in the FX sitcom It's Always Sunny in Philadelphia now in its third season.

She has had a recurring role as Hartley Underwood, the "one-armed" neighbor in the FX series The Riches.

In September 2007, Dan Gross of the Philadelphia Daily News reported that Olson and co-star/creator of It's Always Sunny in Philadelphia, Rob McElhenney, have been dating for over a year. They became engaged in December 2007 to be married in September 2008.