Modifications of thermoplastic starches (TPS) with maleic anhydride (MTPS) and sebacic acid (STPS) were conducted by reactive extrusion to improve compatibilization of TPS/PBAT (poly(butylene adipate-co-terephthalate) blends (50/50). MTPS and STPS were then melt-blended with PBAT in a subsequent extrusion process. The modified TPS was characterized by FTIR spectroscopy and their effects onto TPS/PBAT blends were analyzed by mechanical properties and morphological analyses. The morphological properties were assessed by scanning electron microscopy (SEM). The results obtained from the morphological analysis showed higher phase dispersion of the starch on PBAT, when the TPS was reacted with maleic anhydride (esterification agent). However, the micrographs suggest that sebacic acid does not react with TPS, due, probably, its higher aliphatic chain which may be exuded from the TPS. The mechanical properties of the TPS/PBAT blends, not reacted and reacted with maleic anhydride, presented similar tensile strength, despite the greater dispersed phase distribution of the blend containing MTPS. This result was attributed to the presence of unreacted maleic anhydride, which formed lamellae in the blends, acting as stress concentrator in the blend.