Weaving will join actors Andy Serkis and Ian McKellen on the set of The Hobbit.
The three stars will resume the roles they played in The Lord of the Rings trilogy, those being the characters Elrond, Gollum and Gandalf.
The Hobbit, which is based on the 1937 J.R.R. Tolkien novel, will be adapted to film by Guillermo del Toro, who confirmed that the acting trio is on board for the next instalment.
The story is set to be split into two films, the first opening in December 2011, and the second in December 2012.