An attempt is made to examine the effect of hybrid nanocoolant in microchannel heat sink for computer cooling. Two-hybrid coolants with graphene as one of the prime components are synthesized and images of the particles are shown using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Heat transfer properties like thermal conductivity of the hybrid fluid, specific heat, density, and viscosity are evaluated experimentally and theoretically. The heat transfer characteristics are also studied in heat sink channels of micro level in the processors of personal computers. The parameters like internal heat transfer coefficient, thermal resistances and base temperature representing the processor temperature are examined for the applied heater power of 325 W. The coolant dilution was varied in the range of 0.05 vol%, 0.075 vol% and 0.1 vol% and the base temperature is noted. The recorded lowest base temperature is 310.01 K for the concentration of 0.1 vol% graphene-iron oxide (GFO) system for 0.5 mm fin spacing for the graphene-iron oxide hybrid coolant and for graphene oxide-iron oxide (GOFO) hybrid coolant it is 311.24 K for the same operating conditions. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.