Holland spent the summer of 1999 in the Hamptons of Long Island 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.

The following year, 1999, De Palma took Holland to a theatrical talent agency. Since then she has shot many national commercials. During 2001 when Willa was 10, 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.

After The O.C, Willa starred in her first big movies;Chasing 3000, Garden Party, Middle of Nowhere, Genova and the upcoming 2010 movie Legion. Willa also appeared in a few episodes of Gossip Girl.