Viloft is a novel regenerated cellulosic fibre with a special cross section which creates air gaps in the yarn and improves the thermal properties of the fabric. This fibre is mainly used with the blends of polyester and cotton available on the market. In this study, it was aimed to analyse the mechanical and physical properties of viloft/polyester and viloft/cotton blended ring-spun yarns. For this purpose, five different blend ratios of viloft/polyester and viloft/cotton yarns (100%-0%, 67%-33%, 50%-50%, 33%-67% and 0%-100%) were spun as 19.7 tex on a ring spinning system. The breaking force, elongation (%), unevenness and hairiness results of these blended yarns were analysed using a simplex lattice mixture model. In addition, Tukey's test was also applied in order compare the means of the properties of the blended yarns. Statistical analysis showed that the blend ratio is significant for all the properties of viloft/polyester and viloft/cotton blended yarns. However, Tukey's test indicated that a few of the blends of viloft/polyester or viloft/cotton yarns do not differ from each other. Polyester blended viloft yarns showed higher breaking force, elongation and hairiness, but lower CVm % values compared to cotton blended ones.