Today turbocharging represents a key technology to reduce fuel consumption and exhaust emissions for both Spark Ignition and diesel engines, moreover improving performance. 1D models, generally employed to compute the engine-turbocharger matching conditions, can be optimized basing on certain information about turbine and compressor behavior. Because of difficulty in the correct evaluation of turbine isentropic efficiency with direct techniques, turbocharger turbine efficiency is generally referred to thermomechanical efficiency. To this aim, the possibility to accurately estimate power losses in turbocharger bearings can allow the assessment of the turbine isentropic efficiency starting from the thermomechanical one. In the paper, an experimental and theoretical study on turbocharger mechanical losses is presented. The proposed model, developed in the MATLAB environment, refers to radial and axial bearings.