In this paper, nanocomposite (NC) films of polycaprolactone (PCL)/ZnO-DA were prepared by casting/solvent evaporation method. For this purpose, ZnO nanoparticles were first modified with diacid (DA) based on bioactive amino acid (N-trimellitylimido-l-alanine), at room temperature using methanol as solvent and ultrasound irradiation method. Then, PCL/ZnO-DA NCs were obtained by addition of various weight percentages (2, 4, and 6 wt%) of ZnO-DA into the PCL matrix, under vigorous stirring and subsequent ultrasonic irradiation. The structural characterization of the NC films was carried out using Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. It was found that relative changes in the peaks and morphology were observed, as the concentration of filler was increased. In addition, embedding the NPs into PCL exhibited a reduction in thermal stability of NCs as compared to the pure PCL. FE-SEM and TEM morphological analysis did not show any aggregation of the NPs in the prepared NCs. It was also found that chemical composition of NC films had influenced their optical absorption and mechanical behaviors.