Waterborne polyurethane (WPU) is receiving great attention in recent decades mainly due to the possibility of the replacement of organic solvents by the water. However, this change causes a decrease in the properties (mechanical, thermal, adhesion, among others) of the films obtained by this technique. Therefore, studies have been carried out in the development of polymeric matrix with the incorporation of inorganic fillers. This work presents the synthesis by the in situ polymerization technique and the characterization of waterborne polyurethane/ZnO composites. These composites were based on isophorone diisocyanate, 2,2-bis(hydroxymethyl) propionic acid and a polyester diol (MM = 1,000 g/mol). The filler-polymer interaction, chemical structure, morphology, thermal and mechanical properties of the WPU/ZnO composites were investigated by Fourier transform infrared spectroscopy, Ultraviolet-visible spectroscopy, Thermogravimetric analysis, Differential scanning calorimetry, Scanning electron microscopy and Tensile testing. The results showed an improvement in thermal and mechanical properties of the PU/ZnO composites when compared with pure PU as well as good homogeneity of the filler into the polymer matrix.