Due to climate change, our earth is warming up which directly impacts human thermal comfort. To address this challenge we have developed cooling nano additive as a proprietary mix of several ingredients to promote both cooling action diffusivity and conductivity. Cooling nano additive must be minimum 5% to 8% active addon in viscose multifilament yarn to get perceived skin cooling of -5 to -10 *C. Cooling nano additive has man-made nano particles with precise controlled properties to ensure good spinnability of the viscose multifilament yarn. Fabric or garment has long lasting cooling performance because functional additive is permanently locked in fibre matrix. Cooling nano additive actively changes the thermal resistance, conduction, capacity and insulation properties versus competitive human factors, such as body metabolism and its infrared rays. Based on Q-max factor (0.200 W/cm2) Thermal Effusivity (258.1 W√sec/m2K) , Thermal conductivity (0.1036 W/m.K) tests of 50% Cooling Viscose+50% Polyester fabric, If we use 100% Cooling Viscose then it would exceed the perceived cooling of any previously known technology. The thermal conduction ability of textiles is highly sensitive to humidity and moisture content which depends upon additive content, yarn modification, fabric geometry and garment design. Fabric can be used for high performance applications for summer active wear, fashion, bedding, garments, car seat fabrics etc. Cooling nano Additive is biocompatible and safe enough to human body