Holland was born in Los Angeles, California, the daughter of cinematographer Keith Holland and actress Darnell Gregorio-De Palma. She has two sisters, Brianna Holland (born 1988) and Piper De Palma (born 1996). Holland spent the earlier part of her childhood in Chelsea, London. It was during that period that she spent time on the set of the film Mission: Impossible which was directed by her stepfather Brian De Palma.

She went to Paul Revere Middle School.

Holland spent the summer of 1999 in The Hamptons with her family. After a day playing at Steven Spielberg's home, the seed was planted that she should spend her life acting in film. Spielberg told her mother "You've got to put her in front of a camera!".

Upon her return to Los Angeles that September, Holland first signed with Ford Modeling Agency. She began getting work immediately: her first job was for Burberry of London, where she had much success.

The following year, 1999, De Palma took Willa to a theatrical talent agency. Since then she has shot many national commercials. During 2001 when Willa was ten, she worked alongside her cinematographer father in Ordinary Madness. She was even slated to co-star in the 2005 FOX series The Inside with fellow model Rachel Nichols, but left the show when writer Tim Minear was brought in to overhaul it. She played the role of Kaitlin Cooper on The O.C. for its third and fourth seasons. Incidentally, Willa Holland was a fan of The O.C. before landing the role of Kaitlin Cooper, Marissa Cooper's (Mischa Barton) rebellious "little" sister. She was a regular on the entire fourth season. Willa currently attends private acting classes with one of LAs most esteemed acting coaches.

She has recently graced the cover of Teen Vogue (where she was the youngest cover girl) and Fashion 18 and has been featured in CosmoGirl!, as well as representing LeSportsac Fall and Winter 2006 The O.C. handbags for Macy's. She also currently tops the High Critic's Top 20 list for 2007.

Willa plays a confused teenager (April) in the forthcoming film Garden Party (film) opening July 11, 2008 in Los Angeles, New York, Portland, and Seattle.