Abstract: The thermal conductivity measurement of electrically conducting copper nanofluid is addressed. The measurement principle is based on the transient hot wire method. A platinum wire coated with a thin electrical insulation layer is used as a heating element as well as a temperature sensor. The microcontroller based data acquisition system is provided for data sampling and processing of temperature of the sample with high sampling rate. The copper nanofluid is synthesized by reduction of copper sulfate with sodium borohydride in water without inert gas protection. It is found that the size of copper nanoparticle is 48nm from XRD analysis. The conductivity of nanofluid is measured after calibrating the device with distilled water and ethylene glycol. The enhancement of thermal conductivity is found to be 50.4% over the distilled water for the 1.0 vol. % copper nanofluids