Films from blends of polyurethane and nano-polytetrafluoroethylene aqueous dispersions (PU/nanoPTFE) were prepared, and the effect of the addition of different amounts of PTFE nanoparticles (50 nm) was studied. The changes in the superficial properties of the films were studied by means of XPS, ATR/FTIR, and contact angle measurements. SEM and TEM results are also included. The contact angle values confirm the surface hydrophobicity of composite films. Even though nanoparticles are present in the bulk, higher concentrations of particles appear at the surface in samples with lower nanoPTFE content (up to 10 wt%), as revealed by XPS. Higher amounts of nanoPTFE particles cause aggregation. The mechanical and thermal properties of composites are also discussed.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasCentro de Investigación y Desarrollo en Tecnología de Pinturas