Kathryn Layng was born in Rockford, Illinois. She was a member of the original Broadway company of M. Butterfly. Other New York stage credits include lead roles in The Delusion of Angels and Cinderella Waltz.

Regionally, she originated roles in David Henry Hwang's Bondage at the Louisville Humana Festival, Michael Weller's Buying Time at the Mark Taper Forum New Works Festival, and Keith Reddin's You Belong to Me at the Act One Festival. Her film work includes The Marrying Man and Traveller's Rest, and she has guest-starred on the television episodics Pros & Cons, Joe's Life, Diagnosis: Murder, and New York News.

For four years, she appeared as Nurse Curly Spaulding on Steven Bochco's ABC series, Doogie Howser, M.D., opposite Neil Patrick Harris.

She is married to playwright David Henry Wang.