The studio spent months testing different actresses for the lead role in the film, including Naomi Scott and Shailene Woodley, before selecting Robertson.
She will play Casey Newton, a high schoo girl with a special understanding of technology. She turns to Clooney's character to help her on her quest to save Earth.
Robertson, a 23-year-old American actress, has held a number of roles both in film ("Dan in Real Life", "Scream 4") and TV ("Life Unexpected," "The Secret Cricle"). She is repped by Innovative Artists.
Most details about the script of "Tomorrowland", written by Damon Lindelof, Brad Bird and Jeff Jenson, have been kept under wraps. Hitfix did offer these prognostications. Bird, who made "The Incredible" and "Mission: Impossible — Ghost Protocol," will direct the movie.