In this study, the thermo physical properties of the nanofluid obtained with prepared solution by adding as basic fluid 1.3% the diatomite nanoparticles into water were determined. Many researchers are working to improve the performance of heat transfer fluids. One of the methods used, if we want to increase the overall thermal conductivity of the fluid, the high thermal conductive materials such as metal oxides, metals and carbon should be added to heat transfer fluids as nano‐sized particles. In this study, specific heat capacity, thermal conductivity and viscosity of nanofluid obtained with diatomite nanoparticles in order to increase the fluid's thermal performance and not found in the literature were investigated experimentally.