Amphiphilic starch at different degree of substitution (DS) was prepared by phosphorylation and octenylsuccinylation of acid-thinned starch with sodium tripolyphosphate and 2-octenylsuccinic anhydride, respectively for improving the adhesion of starch to polyester fibers. Various assessment of starch such as H-1 NMR and FTIR analysis, apparent viscosity, starch clarity, adhesion to polyester fiber, desizing efficiency and biodegradability were conducted. The H-1 NMR and FTIR spectroscopy revealed that octenylsuccinate and phosphate substituents have been attached to the molecular chain of starch. Also, the apparent viscosity, paste clarity, desizing efficiency and biodegradability of the amphiphilic starch increased as the DS of phosphate increased. It was observed that the amphiphilic starch was an effective method for stronger adhesion unto polyester fibers but reduced at the highest DS of phosphate due to excessive hydrophilicity. As compared to acid-thinned starch, the stronger adhesion of the amphiphilic starch was attributed to the steric hindrance caused by the two substituents on starch and the good dispersibility impacted by the phosphate substituents on starch. Conclusively, the strongest adhesion on polyester fibers, good paste clarity, good desizing efficiency and enhanced biodegradability of starch were attained at phosphate and octenylsuccinate DS ratio of 0.031/0.014.