Judge Patricia McMahon began her career as an associate at Foley & Lardner, providing pro bono representation to low-income clients. She left Foley in 1970 to become a staff attorney at Freedome Through Equality, the forerunner of Legal Action of Wisconsin (LAW). In 1978, she became Executive Director of LAW. In 1983, she asked to step down to Associate Director in order to engage in more direct client representation.
She has served on the Board of Directors for Rosalie Manor, Migrant Legal Action Program, and the Wisconsin Trust Account Foundation. Judge McMahon has served as a Circuit Court Judge in Milwaukee since 1985.
Judge McMahon retired from the Milwaukee County Circuit Court in 2010.