Kathy Najimy was born and raised in San Diego, California. She is the daughter of Samia (Massery) and Fred Najimy, a postal worker, both of Lebanese ancestry. Kathy attended Crawford High School, and began her film career in the early 1990s, with several minor roles. Kathy got her breakthrough screen role as "Sister Mary Patrick" in Sister Act (1992). She reprised this role in 1993 in Sister Act 2: Back in the Habit (1993). She is most notably known as the voice of "Peggy Hill" on King of the Hill (1997), She is voiced by Goosey in Rugrats.
Kathy lives in Los Angeles with her husband, actor/singer Dan Finnerty (the Dan Band) and their daughter, Samia Najimy Finnerty.