An organopolysiloxane graft-type polyester is prepared by reacting, in the presence of an effective amount of a hydrosilylation catalyst, a polyester containing at least one alkenyl group and having no unsaturated terminal groups, said polyester having a number average molecular weight of about 500 to about 5,000, and an organopolysiloxane containing one hydrosilyl group. The organopolysiloxane graft-type polyester has excellent compatibility with polyesters and can improve the surface smoothness and hydrophobic property of the polyester when modified therewith.