Structural study of two grafted polyesters, which were different in mechanical properties, was investigated by DMA, TEM, and high-resolution solid-state C-13- NMR. Using DMA and TEM, a separated phase larger than 100 nm was not found in the grafted polyesters. The main chain and the side chain seemed miscible. Analysis of T(1 rho H)s and their distributions made the difference of microstructure in the grafted polyesters clear. P(EA-AA)-grafted polyester, which was very brittle, had a separated phase in the grafted polyester. The separated phase was estimated to be at a size of about 3 nm. On the other hand, P(St-DEF-Manh)-grafted polyester, which was very ductile, had a homogeneous microstructure. The difference in the microstructures of the grafted polyesters seemed to effect the mechanical properties of the grafted polyesters.