One of the most harmful environmental contaminants is thought to be crude oil. Polycyclic aromatic hydrocarbons (PAHs) are thought to be among the most significant and hazardous petroleum molecules that are released into the environment. Currently, one of the most significant and ecologically beneficial methods for treating these toxins is bioremediation. Therefore, the purpose of this study was to find out how well the fungus Aspergillus terreus Thom, which was isolated from a soil that had been heavily contaminated by oil, could biodegrade the polycyclic aromatic hydrocarbons found in Basrah heavy crude oil. It was also determined how various factors affected this fungus capacity for biodegradation. Findings revealed that following a 15-day incubation period, A. terreus, degraded 43% of the crude oil, and this percentage was increased to 75% after 30 days of incubation. GC-MC analysis revealed that A. terreus had a good ability to degrade PAHs, and the residual total PAHs reached to 755 µg mL^-1 after 15 days and decreased to 491 µg mL^-1 after 30 days compared with the control with 1006 µg mL^-1 PAHs. Three compounds  namely napthalene, acenaphthnen and fluorene, were completely degraded. The temperature 30 °C and pH 5.5 were the optimum conditions for degradation. The degradation percentage reached to 29%, and the total PAHs concentration was decreased to 397 µg mL^-1 after 7 days of incubation at the optimum conditions. Two aromatic compounds viz. napthalene and fluorene were completely degraded after 15 days and the concentration of PAHs was decreased to 235 µg mL^-1. Hence, A. terreus exhibited the potential for the degradation of PAHs.