The main goals of this study were to determine the effect of three yarn structural factors (yarn count, cross section and spandex ratio) and their interactions on tensile and breaking extension properties tensile behavior effect of spandex/polyester spun yarns respective on woven fabrics. Moreover, stress-strain curves were plotted and the yield points and breaking points and their corresponding properties (toughness, stiffness and Initial Young Modulus) were derived. The association between tensile and elongation parameters for spandex/polyester yarn and their woven fabrics was computed using simple correlation coefficient, results explained that all tensile and breaking extension properties significantly increased as the yarn count increased while the effect of cross section was weak or marginal. It is obvious that yield strain, yield stress, breaking extension, breaking tenacity decreased as a result of increasing the spandex content but the decrease percents (%) were generally weak. With respect to the 1st and 2nd order interaction effects, they were no significant for most tenacity and elongation properties of spandex/polyester spun yarns and their respective woven fabrics. The current study appeared that using spandex/polyester spun yarns with lowest spandex content gave the best tensile and breaking extension properties of spandex/polyester spun yarns and their respective woven fabrics. The correlation coefficients between tensile and elongation parameters for spandex/polyester yarn and their corresponding woven fabrics were positive and highly significant (except Initial Young's modulus) indicating that the tensile and breaking extension properties of the spandex/polyester yarns could be used as good indicators for the strength and elongation of fabrics manufactured by these spandex/polyester yarns.