A modified polyimide represented by Formula 4: wherein D is a heat curable or photocurable functional group, R is a divalent or higher polyvalent organic group, and n is an integer of 1 or greater, X1, X2, X3, and X4 are each independently a tetravalent organic group derived from a tetracarboxylic dianhydride, Y1, Y2, and Y3 are each independently a divalent organic group derived from a diamine, p, q, r, and v are each independently an integer of 0 or greater, with the proviso that p, q, r, and v are not simultaneously 0, and r+v is 1 or greater. Additionally, curable resin compositions including the modified polyimide, as well as polyimide films including a cured product of the curable resin composition, and methods for preparing the modified polyimide.