In September 2003 Munn won a co-starring role opposite Amanda Bynes and Jennie Garth in the second season of The WB sitcom What I Like About You as Tina Haven, Holly Tyler’s new best friend. Although their characters were the same age, Munn is eleven-and-a-half years older than her co-star Bynes. Munn remained on the show until the show ended with the fourth season on April 24, 2006. Munn also had a recurring role as Caroline, Fez’s borderline stalker girlfriend on the Fox sitcom That ’70s Show.

Munn began dating her childhood friend, actor Scott Holroyd, in 2004. They became engaged in Paris in December 2006 and married on November 17, 2007, at the French Huguenot Church in Charleston, South Carolina. They reside in Los Angeles with their pet terrier, Buster Keaton. In November 2011 Munn announced the birth of their son via her Twitter. She gave birth to their daughter in 2015.

Munn co-starred as Cindy in the short-lived ABC sitcom Carpoolers that ran from October 2, 2007 to March 4, 2008. In 2009 Munn began a recurring role on The WB drama One Tree Hill playing Lauren, Jamie Scott’s teacher who begins to date Skills Taylor at the end of the sixth season.

From 2014 to 2018, Munn co-starred opposite Brian Stepanek as Anne Harper, the mother of the titular quadruplets in Nickelodeon sitcom Nicky, Ricky, Dicky & Dawn.

In 2017 Munn joined her former One Tree Hill castmates in signing a letter of support for one of the show’s writers, who had accused One Tree Hill’s showrunner of sexual harassment.