The thermal performances of a minichannel heat sink are experimentally investigated for cooling of electronics using nanofluid coolant instead of pure water. The Al₂O₃–H₂O nanofluid including the volume fraction ranging from 0.10 to 0.25 vol.% was used as a coolant. The effects of different flow rates of the coolant on the overall thermal performances are also investigated. The flow rate was ranged from 0.50 to 1.25 L/min as well as the Reynolds number from 395 to 989. The coolant was passed through a custom made copper minichannel heat sink consisting of the channel height of 0.8 mm and the channel width of 0.5 mm. The experimental results showed the higher improvement of the thermal performances using nanofluid instead of pure distilled water. The heat transfer coefficient was found to be enhanced up to 18% successfully. The nanofluid significantly lowered the heat sink base temperature (about 2.7 °C) while it also showed 15.72% less thermal resistance at 0.25 vol.% and higher Reynolds number compared to the distilled water