In 2014, she began playing the female leading role in the CBS procedural drama NCIS: New Orleans. McLellan later guest-starred on House and The Mentalist, and also had roles in Lifetime TV movies. The series was canceled after two seasons in 2009. After the series ended, McLellan was cast as the wife of Peter Krause's character, in the ABC soapy comedy-drama series Dirty Sexy Money. For the final season of the show she was elevated to series regular. In 2001, McLellan joined the cast of CBS procedural JAG, in a recurring role as Navy Petty Officer Jennifer Coates. In 2000, McLellan had her first major movie role, in the fantasy film Dungeons & Dragons. In 1995, she began her career on television, appearing over the next five years on episodes of Sliders, Diagnosis: Murder, and Star Trek: Voyager.
