In "Harry Potter and the Deathly Hallows", Flitwick insists that Rowena Ravenclaw's Diadem is lost, and he is described by Harry (along with Dumbledore) as having been a "model student" who supposedly never entered the Room of Hidden Things, and so it never occurred to him that the diadem could be hidden there. Before the Battle of Hogwarts, Flitwick helps to chase Severus Snape out of the Hogwarts castle alongside professors McGonagall and Sprout, and to put protective charms around the castle to hinder Voldemort and his oncoming Death Eaters, and later fights the intruders in the battle, battling Corban Yaxley and later defeating Dolohov.