ABSTRACTThe use of single-core elastic spun cotton yarns is well established in textiles and denim industry but interest in the use of dual-core-spun yarns has started to grow only recently. The aim of this study was to investigate the effect of polyester and elastane linear density on the physical and mechanical properties of dual-core-spun cotton yarns. Yarn samples were prepared on industrial-scale spinning machines using cotton as the sheath fibers and two different linear densities of polyester and three different linear densities of elastane filaments in the core. Statistical analysis of the results revealed that yarn tenacity, elongation, uniformity, and hairiness are significantly affected by the linear densities of both the polyester and elastane filaments in the core, with statistically significant interaction between them. Yarn imperfections (IPI), however, are affected mainly by the polyester denier, while the elastane linear density did not show statistically significant effect on the IPI. Regression equations for different yarn properties were also developed which showed fairly high values of coefficient of determination (R-sq).