She is known for playing Hermione Granger in the Harry Potter movie series alongside Daniel Radcliffe and Rupert Grint . Watson was cast as Hermione at the age of nine , having previously acted only in school plays . From 2001 to 2010 , she starred in seven Harry Potter films alongside Daniel Radcliffe and Rupert Grint ; she will return for the final installment : the second part of Harry Potter and the Deathly Hallows .