Poly(1,4-butadiene)-graft-poly(L-lactide) copolymers were efficiently prepared via the grafting-from strategy using a combination of ring-opening metathesis polymerization (ROMP) of a hydroxyl-functionalized cyclobutene monomer and organocatalyzed ring-opening polymerization (ROP) of L-lactide. The copolymers were characterized by NMR, MALDI-TOF, SEC, TGA, and DSC demonstrating that well-defined polyester-grafted poly(1,4-butadiene) were obtained through the reported methodology.