Mara was born on Feb. 27, 1983 in the Westchester County, NY town of Bedford. There, she was raised along with three siblings - older brother Daniel, younger sister Patricia and younger brother Conor - by the parents of an NFL dynasty. Mara's father, Chris Mara, was a VP of player evaluation for the New York Giants. Her grandfather, Wellington, owned the team, which her great-grandfather Tim originally founded. On her mother's side, Mara's great-grandfather, Art Rooney, was equally established in the sport, having founded the Pittsburgh Steelers.
Kate graduated from high school a year early. She was accepted at the prestigious NYU Tisch School of the Arts but deferred for 3 consecutive years due to acting and singing.
She is the great-granddaughter of the founder of the New York Giants, Timothy Mara and Art Rooney, founder of the Pittsburgh Steelers. She often sings the national anthem at Giants home games.
Kate made her television debut in 1997 in "Law & Order" and made her film debut in 1999, at the age of fourteen, in the film "Random Hearts." She has had reoccurring parts on the TV shows "24" and "Nip/Tuck," and her movie credits include "Brokeback Mountain," "The Californians" and "We Are Marshall." Kate is the granddaughter of the late New York Giants owner Wellington Mara.