Nano-TiO2filled polypropylene was compounded on a twin-screw extruder and diluted to a filler con-tent of 1 vol.-%. Nanocomposite and neat matrix material were then injection molded to plates and vibration welded. Thin films of welded specimens were investigated in micro-tensile testing under the light-microscope in order to achieve global and local tensile properties and compared to results of tensile tests for two welding pressures on neat and filled polypropylene. Based on investigations, a model of the welding area has been created with ANSYS, which then was coupled and compared with experimental results based on macroscopic test coupons. Prediction of break position based on stress distribution calculated in the model was in good agreement with experimental results.