The interaction of microwave radiation with Partially Oriented Polyester yarn (PET-POY) was studied with a view to improve its structure and textile related properties. The PET-POY filaments were exposed to Microwave (MW) radiations of frequency 2450 MHz for different durations of time from 15 to 105 sec. The changes in structure and morphology were investigated by using the techniques of X-ray diffraction, birefringence and DSC. The changes in the textile related properties like tensile strength, shrinkage and dye uptake were evaluated. The microwave treatment enhanced the structural properties of PET-POY samples. Significant increase in crystallinity, crystal size and crystalline orientation were noted. In addition a great improvement in total orientation, as measured by birefringence, was found for the treated samples. DSC results showed that crystal distribution became narrower and crystallization rate increased for microwave treated samples as compared to control sample. The tensile strength, shrinkage and dye uptake also showed significant increase, which is very helpful for the textile processes.