This paper presents an experimental study of the seam performance of PET/nylon-elastane woven fabrics. In this study, plain and twill fabrics were woven with three different weft densities. Two different sewing threads were used during he sewing of the fabrics. Therefore, 12 samples having different specifications were obtained. For these fabrics, nylon-elastane air-covered yarn was used as the weft yarn and PET air-covered yarn was used as the warp yarn. Seam strength, seam slippage strength, sewing needle penetration force and seam efficiency were determined for these fabrics for seam performance. The purpose of this study was to identify the suitable sewing conditions in order to achieve good seam performance. This study also investigated the effects of weft density, weave type and sewing thread on the seam performance.