The application of polymeric materials has become an indispensable need in various sectors of industry and agriculture. Excessive consumption of petroleum-based materials, which leads to the depletion of natural resources, has prompted scientists to explore new biodegradable materials that can be used for the various needs of the industry. Biodegradable materials have the ability to decompose in the environment under the influence of microorganisms, water, oxygen and sunlight. In addition to the positive impact on the environment, certain biodegradable materials such as thermoplastic starch (TPS) are economically advantageous due to their affordability, availability and ability to reduce the market's dependence on plastic prices dictated by the oil industry. In this study, the biodegradability of polymer mixtures consisting of thermoplastic starch and polylactide (PLA), with and without the addition of citric acid (LK), was examined. The test was conducted in accordance with ISO 14855 and ASTM D5338 standards. The identification and characterization of TPS/PLA mixtures that are biodegradable was thoroughly carried out using Fourier transform infrared spectrometry (FTIR-ATR). The morphology of polymer mixtures was analyzed using scanning electron microscopy (SEM). Samples were observed before and after the biodegradation process by light microscope and optical microscope with polarization for insight into the surface structure of the material. A change in mass during the 56 days of the biodegradation process was also monitored.