Marine plastic pollution has become a major global environmental concern. Plastics released into marine environments undergo gradual weathering, driven by physical, chemical, and biological processes, such as ultraviolet exposure, wave action, oxidation, and microbial colonization.  While extensive research has focused on physical and chemical degradation, the role of marine microorganisms in plastic weathering remains relatively under-explored. This study investigated the microbial contribution to the early-stage weathering of polyvinyl chloride (PVC), a polymer known for its high environmental persistence. Marine bacterial, cyanobacterial, and fungal strains commonly identified in the plastisphere (e.g., Sphingomonas aestuarii, Alteromonas macleodii, Polaribacter marinaquae, Synechococcus  sp., and Penicillium citrinum) were used for experimental exposure to PVC films under controlled seawater conditions. To evaluate the weathering dynamics, a three-tiered analytical framework was employed. Biological interactions were first characterized by visualizing microbial colonization via fluorescence microscopy, accompanied by quantitative analysis of biofilm and qPCR-based assessment of microbial abundance. Surface-level physicochemical alterations were subsequently probed using a suite of advanced spectroscopy techniques–including Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy–alongside contact angle measurements. Finally, the broader degradation dynamics were assessed by monitoring changes in microplastic particle abundance within the seawater samples. This comparative study provides critical insights into the biological mechanisms driving marine plastic weathering and highlights the significant contribution of microorganisms to early-stage degradation.