The influence of thread structure and lubrication ratios on sewing performance of polyester multifilament, staple and core-spun threads with 2%, 4% and 6% lubrication ratios has been studied. Three different twists (540 twists/m, 635 twists/m and 1060 twists/m) were applied to 100% polyester yams to analyze the effect of twist. The multifilament polyester yarns with 2 and 3 plies were used to study the effect of ply numbers. The effect on breaking elongation, coefficient of friction between thread and metal, and initial elasticity modulus has also been studied. The seam strength and seam slippage were measured to evaluate seams performance. It has been observed that the structure of threads affects the seam strength, whereas the lubrication ratio, does not. The core-spun thread structure shows a great resistance against the seam opening.