Benson was born in Birmingham, Alabama to psychiatrist, Edward and Diane Benson. She has a younger sister, Danielle who is an artist. As a child Benson studied music and dance, performing in the Birmingham Children's Ballet as well as in local theater. She attended high school in Orlando, Florida but moved to Los Angeles later with her family.
Her first film role was in Steven Soderbergh's King of the Hill at the age of 14.
Benson was cast as shy wiccan Tara Maclay in Buffy the Vampire Slayer in 2000, becoming a popular and important character to the series due to the lesbian relationship she shared with Willow Rosenberg. She left the show in 2002 after appearing regularly for three seasons. She provided singing vocals on the musical episode Once More, With Feeling.
Whilst appearing on Buffy, Benson co-wrote the movie The Theory of the Leisure Class which was released in 2001. She also wrote, produced, directed and starred in digital video Chance which also starred her Buffy co-star, James Marsters.
In 2006, Benson released her second feature-film Lovers, Liars & Lunatics through her own production company, Benson Entertainment. It was shot on film and was mostly budgeted by the the sale of limited edition Buffyverse 'Tara' action figures.
In 2006, she appeared as 'vegetarian' vampire Lenore in Supernatural. She also co-directed 2010 comedy, Drones with Buffy co-star Adam Busch.
Benson and Buffy co-star, Adam Busch dated from March 2009. The couple are no longer together but remain close friends. Benson now lives in Los Angeles, California.
- She loves to read. Her favorite authors include J.K. Rowling and Christopher Golden.
- She shares her birthday with Elvis Presley.
- Wrote a comic book based on the characters of Willow and Tara from Buffy the Vampire Slayer.
- Arrived late to a Buffy convention in 2003 because a deer ran into her mother's car in New York.
- According to Buffy producer Marti Noxon, Joss Whedon was initially reluctant to cast Benson in the role of Tara Maclay due to her not being the right physical type. Noxon convinced him to let her read again where he realized she would be perfect for the role.
- Sang on two tracks on Buffy co-star Anthony Stewart Head's solo music project, Music for Elevators.
- "I got letters from girls saying that I had changed their lives and I met people who would cry about it, and that had such an impact on me. You don't realize what an impact television has on people. But when you get letters from young girls saying "I came out and now I have a girlfriend because of you", it's great." - About her role as lesbian Tara on Buffy The Vampire Slayer
- "I have breasts and hips and I am very happy that they are a part of me. I weight one-hundred-and-eighteen pounds and I'm five foot four. If you saw me in real life, you'd think I was on the thin side." - on being percieved as 'heavy'.