The article deals with effect of the nano-fluids on the performance parameters of heat pipes. Stainless steel heat pipe was filled with a nano-fluid, a solution of copper sulphate and ferric chloride, up to 20% of the total volume of the heat pipe. Solutions of the nano-fluids were produced in the following concentrations: 1%, 2%, 3%, 4% and 5%. The performance parameters were measured on the experimental setup. The experimental measurements were carried out for different operating temperature and measured results show that the concentration of working fluid has effect on performance of the heat pipe.