After graduating with degrees in physical education and dance at Ohio University, Mary Murphy began working as an instructor at a dance studio in Washington D.C. She was inspired to pursue a career in dance after attending the United States Ballroom Championships in New York.
Murphy saw early success at the international dance circuit with partner Manfred Sigletz. However, she decided to stay put in California, and focus instead on her own Champion Dance Academy in San Diego. She later won numerous American competitions with Bill Milner and Jim Desmond, before retiring in 1996 to focus on teaching.
Murphy first joined Fox's So You Think You Can Dance as ballroom choreographer and guest judge in 2005. At the beginning of the third season, she became the show's second permanent judge, thanks in part to her frantic style of critiques, characterized by enthusiastic screams and terms such as the "Hot Tamale Train". She left as a permanent judge in the show's seventh season, partly to recover from throat cancer, but she returned to the show in the following season.