Born in The Bronx, New York, Buono was raised in a blue-collar family and decided at an early age to make acting her life's ambition. At 11, she showed her connection to her family's work ethic by answering a casting call ad for Harvey Fierstein's "Spookhouse" and landing the role, without any assistance from her family or other adults. Buono began landing roles on television and the New York stage while in her teens and early twenties, and earned a Daytime Emmy nomination as a young victim of sexual abuse in Abby, My Love (1991) (CBS, 1991), which aired as part of the CBS Schoolbreak Special (1984). She soon graduated to minor roles in Stephen Gyllenhaal's Waterland (1992), with Jeremy Irons and Ethan Hawke; as an illegal immigrant in The Cowboy Way (1994), with Woody Harrelson and Kiefer Sutherland; and in Noah Baumbach's much-loved indie comedy, Kicking and Screaming (1995), which reunited her with her "Abby, My Love" co-star, Josh Hamilton. While cultivating her acting career, Buono also graduated from Columbia University with a double major in English and political science in 1995, which she earned in just three years.