The Lord of the Rings and X-Men Origins: Wolverine actor has been cast as an antagonist in the movie, according to Variety.
Raffey Cassidy (Snow White and the Huntsman) is attached to play Molly - a orphan who has the power to hypnotise others - in Amber Entertainment's adaptation of Georgia Byng's children's fantasy novel series.
Monaghan's character is described as a bank robber who will stop at nothing to get hold of a book on hypnotism that Molly owns.
Byng is on board as a producer alongside Amber's Ileen Maisel (Inkheart, The Golden Compass) and Lawrence Elman, while Christopher Rowley (Bonneville) will direct.
Monaghan's forthcoming film projects include thriller Deep Burial and crime drama Monster Butler.
The actor has also made an eight-episode wildlife documentary series titled Wild Things with Dominic Monaghan.
Monaghan recently promised fans in a Twitter post that he will have "official UK [transmission] dates" for the series very soon, and also promised details of international broadcast "by December".