Provided are: a composition for a window film; a flexible window film formed therefrom; and a flexible display device comprising the same, wherein the composition contains: a siloxane resin comprising chemical Chemical Formula 1 or 2 or a mixture thereof; a cross-linking agent; and an initiator, the cross-linking agent being contained in a content of about 10-30 parts by weight on the basis of 100 parts by weight of the siloxane resin or the mixture thereof.