Due to its widespread use in common routine items, plastic is ubiquitous in our daily lives. Its continuous use, accumulation and inadequate disposal of plastic waste pose a serious threat to the biotic and abiotic components of the environment. Microplastics (MPs) are particles of synthetic organic polymers less than 5 mm in size, including those not visible to the naked eye. MPs have become one of the leading threats to the environment due to their persistence, ubiquity and intrinsic toxic potential. The biodegradability of polymers depends on the physical and chemical properties of the polymer, abiotic properties, as well as on the properties of the microorganisms themselves. Biodegradation is one of the most commonly used methods for removing MPs from the environment, but in order to be highly effective, it is necessary to optimize significant process factors. In this paper, the biodegradation of polyvinyl chloride (PVC) particles was researched using the Bacillus cereus bacteria. The aim of this study was to firstly determine the significant factors for the process of biodegradation of MP PVC using Bacillus cereus and then examine the optimal conditions for the process of biodegradation of MP using the mentioned bacterial culture. The experiment was performed according to Full factorial (FF) design in combination for three examined factors - MP size, MP concentration, and optical density (OD) of the prepared bacterial suspension - at three levels (minimum, mean and maximum). During the 30 days of the biodegradation experiment, the change in OD and the total number of grown bacterial colonies (Colony Forming Unit, CFU) were monitored. In the aqueous phase, the values of total (TC), organic (TOC) and inorganic (TIC) carbon were determined. LC/MS analysis monitored the release of additives from MP particles and potentially formed degradation products which formed during the biodegradation of MP. Structural changes in PVC were determined by ATR-FTIR spectroscopy. At the end of the biodegradation process, the ecotoxicity of the filtrate was examined using the Vibrio fischeri bacteria. The experimental results were processed using statistical analysis of variance (ANOVA). The results of the experiment indicate that better growth of the Bacillus cereus bacteria was observed at a mean PVC concentration of 500 mg/L, a mean particle size of 300-500 μm and a maximum OD of 0,5. In view of the above, the tested bacterial culture has the ability to biodegrade MPs.