Plastic polymers are petroleum-derived synthetic materials that have multiple uses in everyday life, but their excessive production has led to the accumulation of approximately 1,000 million tons of residues, causing negative ecological impacts. This study analyzed the biological degradation in liquid medium of polyurethane, polystyrene, and polyethylene samples by filamentous fungi isolated from Antarctica. The plastic samples were used without pretreatment or pretreated with an artificial aging UV chamber according to ASTM G155 for 500 h, inoculated or not with the Antarctic fungi (Penicillium, Geomyces, Mortierella species). Samples were incubated at 18°C for 90 days to determine potential fungal biodegradation. The physical-chemical and biological degradation of plastics were evaluated by analyzing the weight loss in function of time, and by determining possible changes in the chemical structure, using the technique of Fourier Transform Infrared Spectroscopy (FTIR). The polymers exposed to the artificial aging chamber resulted in the oxidative degradation of plastics (detected by morphological and structural changes), which favored their biodegradation. Out of the three fungal strains, Penicillium spp. presented the highest degradation percentage in aged plastics corresponding to 28.3% in polyurethane, and to 8.39 and 3.53% in polystyrene and low-density polyethylene, respectively.