Nicholas Brendon was born three minutes after his identical twin brother, actor Kelly Donovan on April 12, 1971 in Los Angeles, California. He attended Chatsworth High School, where he struggled with stuttering but was also a starter on the baseball team. He had dreams of playing for the L.A. Dodgers, but had to pursue other options when he hurt his arm about a year after graduating high school.

He got his big break as an actor when he landed the role of Xander Harris on the hugely successful TV series Vampir Avcısı Buffy (1997). The series ran from 1997 until 2003, garnering a huge cult following as well as a large fanbase for Brendon. Brendon and brother Kelly appeared together in the episode "The Replacement", in which Xander has to cope with having a seemingly sinister double. His first major role in a feature film came with the Charles Busch satire Psycho Beach Party (2000). Brendon has also starred in the ABC Family Channel original movie Celeste in the City (2004). Brendon is a spokesperson for the Stuttering Foundation of America, appearing in a print campaign for the organization.