Katherine Kiernan Mulgrew was born on April 29, 1955 in Dubuque, Iowa, the second oldest of eight children. At the age of twelve, Kate expressed an interest in acting. Her mother brought home biographies of some of the greatest actresses, and enrolled Kate in summer acting schools. Kate took on her first job at the age of 13, and became financially independant at 16, working at diners to put herself through school. When she was 17, Kate enrolled at New York University, but left after her junior year to pursue acting full time after being accepted into Stella Adler's Conservatory.
Kate was quickly cast as Mary Ryan on the ABC Soap Opera Ryan's Hope, and stayed with that role for about two years. At 23, she was approached by Fred Silverman, the head of programming for NBC, and was offered the lead role in "Mrs. Columbo", a series actually created for her. She starred as "Kate Columbo", wife to the famous "Lieutenant Columbo", played by Peter Falk. The series was a success, but was eventually cancelled, and syndicated under the name Kate loves a mystery. In 1979, she received a Golden Globe Award nomination for 'Best Dramatic Actress in a Series' for her work on "Mrs. Columbo."
Kate went on to star in several feature films, including Love Spell: Isolt of Ireland with Richard Burton, A Stranger Is Watching alongside Rip Torn, and Remo Williams with Fred Ward and Wilford Brimley. She also traveled to Europe to film The Manions of America, an ABC Mini-Series also starring Pierce Brosnan. She also starred in Throw Momma From the Train with Danny DeVito.
In 1994, Kate was about to sell her house, when she got a call from Paramount. The lead (Genevieve Bujold) on a new Star Trek series had bailed, and the role of Elizabeth Janeway needed a replacement. Fighting a case of the flu, Kate went to the studio anyway, and landed the role. The character's name was then changed to Kathryn.
She currently lives in California with her two sons Alec and Ian, and her dog Gracie.