This study investigates the biodegradation potential of two fungal strains, Aspergillus niger and Trichoderma harzianum, on polyethylene plastic bags, addressing the environmental challenges posed by the resistance of the plastic material to degradation. The fungi were cultivated, and their spore suspensions were tested for polyethylene degradation in both the soil and liquid salt media. Degradation was assessed using weight loss measurements, thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). After one month in liquid medium, A. niger induced a 45.62 ± 0.21% weight loss of polyethylene, while T. harzianum achieved a 36.0 ± 0.21% weight reduction. In soil, weight losses of 9.09 ± 0.08% and 10.00 ± 0.18% were observed after two months, respectively. TGA confirmed that the fungus-treated polyethylene samples were less thermally stable than untreated controls, indicating successful biodegradation. FTIR analysis revealed structural changes in the degraded polyethylene, while SEM images demonstrated significant surface alterations, including pitting, roughening, cracks, holes, and fungal colonization. These findings confirm the enzymatic action of fungi in degrading polyethylene into monomeric forms. The study highlights the potential for fungal biodegradation as an environmentally friendly strategy to mitigate plastic pollution. Future studies should characterize the specific enzymes involved and explore genetic engineering to enhance degradation rates.