Harmon began acting in 1995 after being discovered on a plane by David Hasselhoff. She then starred in several television series, including Baywatch Nights, Baywatch and C-16: FBI. She also appeared in the 1998 film, Lawn Dogs, which received only a limited theatrical release. In the late 1990s, Harmon became better known by joining the long-running NBC series Law & Order, playing ADA Abbie Carmichael from 1998 to 2001. During this time, she also voiced Barbara Gordon in the animated film Batman Beyond: Return of the Joker*, succeeding Stockard Channing in that role.

Harmon left Law & Order to concentrate on her film career, saying that she preferred working in film to television. After appearing in the 2001 direct-to-video film Good Advice, she had a supporting role in Agent Cody Banks, playing the CIA handler of a teenage agent (Frankie Muniz). In 2006, Harmon co-starred with Cuba Gooding Jr. and James Woods in the direct-to-DVD political suspense drama End Game.

In 2006, Harmon starred in an ABC pilot Secrets of a Small Town, which did not go to series. She also starred in another failed television show on NBC, Inconceivable, which was canceled after two episodes. The following year, she starred in another ABC pilot, Women's Murder Club*. The police drama was picked up, but only ten of the thirteen episodes aired.

Harmon was one of five actresses who posed discreetly nude for the May 2008 issue of Allure magazine, alongside Gabrielle Union, Zoe McLellan, Jill Scott, and Ana Ortiz.

In 2010 Harmon hosted an infomercial for "UpLiv", a stress management program and also appeared in an infomercial for Olay "Pro-X" wrinkle cream.

From 2010 to 2016, she co-starred with Sasha Alexander in the TNT crime-drama series Rizzoli & Isles, playing Boston, Massachusetts police detective Jane Rizzoli. The show premiered July 12, 2010. She directed the series' 100th episode.

Harmon appears in the music video for Craig Morgan's "This Ole Boy", released in January 2012.

In July 2012, during promotions for a new season of Rizzoli and Isles, Harmon revealed on Conan O'Brien's late night series that she was a fan of and very interested in playing a movie version of the She-Hulk from Marvel Comics should such a movie become available.

Harmon won Outstanding Female Actor in a Leading Role in a Drama Series for Rizzoli & Isles at the 2012 Gracie Allen Awards.

Models, Television Personalities, Actors, Entertainers, Media Professionals, Motherhood, Television Actress, Actress, For Christian and Faith based events, Christian, Christian Women, Conservative, North Carolina, Republican Party, Celebrity Political, Acting, Modeling,