Kathy got her first education at the Crawford High School, located in the El Cerrito neighborhood of San Diego. Any information about her childhood is unavailable on the internet, and first mention about her career was in 1985, when she was 28. According to the official records, her first episodic role was in the comedy-romance film Walls of Glass. Then in early 90s she had also several episodic or minor roles in Soapdish (as Tawny Miller), The Hard Way (as Lang's "Girl Friday") and The Fisher King (as a video customer).

The first noticeable work was in 1992, when she was invited to play Sister Mary Patrick in a comedy film Sister Act. That was her first major role and she coped with it very well. She worked there along with a star of comedy genre Whoopi Goldberg. The film was very profitable (with a budget of 31 million dollars and box office 231 million dollars), so it is not surprising, that in 1993 Touchstone Pictures released the sequel Sister Act 2: Back in the Habit. This time main roles apart from Whoopi Goldberg played Maggie Smith, Kathy Najimy and Wendy Makkena. The sequel was not as successful as the first release (only 57 million dollars box office) but for Kathy Najimy it was very beneficial, since she became a professional actress.

After this breakthrough role, she played in a numerous films, namely Hocus Pocus (1993), In Search of Dr. Seuss (1994), Jeffrey (1995), Hercules (1998), If These Walls Could Talk 2 (2000), Rat Race (2001), How to Fall in Love (2012) and many other.

Apart from films, she voiced a lot of animated films, including animated musical comedy film Cats Don't Dance, where she voiced Tillie Hippo and her character was singing. That animated film also voiced such famous actors such Scott Bakula, Don Knotts and Jasmine Guy.

With an experience of voicing in animated films, Kathy Najimy was hired by Fox to voice Peggy Hill in their adult animated TV series King of the Hill. Kathy has worked on that project from 1997 to 2010, and this series became her the most long-termed work. Her other long-termed part was in TV sitcom Veronica's Closet, aired on NBC, where she played Olive Massery. During her career participated in 64 movies, TV series and animated films in total. This allowed her to earn a fortune. Her net worth is estimated to be four million dollars.

On the Internet, you can find many memes, which portray Kathy’s life as an activist. She fight for the women rights, human rights and gay rights. She also fight against prejudice about the weight of women. She often calls not to pay so much attention to weight loss of women.

As for her personal life, she is married to Dan Finnerty and they have a mutual daughter Samia. To find out more about her biography visit her page on Wikipedia.