Katie won a Tony Award and the Drama Desk Award for Best Featured Actress in a Play in 2002 for her role as Brooke Ashton in the Broadway revival of Noises Off.

She played a "lovely but dim fashion model" in the original Broadway production of Neil Simon's Proposals in 1997–98, Sally Bowles in the 1998 Broadway revival of Cabaret (from November 21, 2000 to January 18, 2001), and call girl Cora in the 1999 Broadway revival of The Iceman Cometh, opposite Kevin Spacey. She also has appeared in My Favorite Year with Tim Curry, John Guare's Bosoms and Neglect, and Smell of the Kill, with Kristen Johnston.

Finneran's biggest film role to date may be Judy Rose in the remake of George A. Romero's Night of the Living Dead. Her film credits include You've Got Mail, Chicken Little, Liberty Heights, Bewitched, Miss Congeniality 2: Armed and Fabulous, and Death to Smoochy.

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