Sport wears almost preferred with knitted fabrics especially interlock construction. However there is a need for higher comfortability and functional properties for fabrics to be more fitted to this application. This study compared cotton and polyester microfibers and blended them to improve the functional activity of interlock in sport wear by mercerization, also fabrics dyeability are affected by mercerization. Knitted cotton, polyester microfiber fabrics and polyestermicrofibre cotton blend are knitted on interlock knitting machine. Then fabrics have been mercerized with sodium hydroxide to enhance many functional properties. This process improves dyeability with both reactive and cationic dyestuffs. The dyeing process providing all treated fabrics many functional properties such as UPF protection. The changes in different mechanical as well as physical properties were investigated. The washing fastness properties of the dyed fabrics are also given. The overall moisture management capacity (OMMC),burst strength, air permeability, coefficient of friction, surface roughness, and thermal conductivity were measured for blank fabrics, after washing, after washing and mercerizing, after dyeing washed fabrics, and after dyeing washed mercerized fabric. Significant differences for overall moisture management capacity (OMMC), bursting strength, air permeability, coefficient of friction, surface roughness, and thermal conductivity were found between blank fabrics and all different finished fabrics under study. 100%cotton fabric has the highest thermal conductivity, and flexural rigidity in blank stage and all finishing and dyeing stages, while microfiber polyester fabric has the highest air permeability and coefficient of friction in blank stage and all finishing and dyeing stages .