Light weight fabrics are selected for their aesthetic qualities, drape, and handle. But these fabrics are difficult to sew. Seams are the basic elements in a structure of any apparel. Seam performance affects the quality of the apparel product. In this research seam performance of two kinds of light woven fabrics differs in their construction (chiffon and satin) were studied in terms of seam strength, efficiency, and seam strain. The effect of some sewing parameters (sewing thread count, stitch density, needle size, stitch type) on seam strength, efficiency, and seam strain were investigated. Regression equations which can predict each of the previous parameters were concluded in both warp and weft directions. It was found that the stitch density and the interaction between thread count and stitch type affect warp seam strength for both chiffon and satin fabric. Sewing thread count has significant effect on seam stress in both directions for both fabrics under study. Also it affects seam strain in warp direction for satin fabric. The significant effect of sewing needle count on seam performance appears only in seam stress in warp direction for chiffon fabric.