Abstract: The effect of levels of sun flower oil and storage period on quality of mozzarella cheese was investigated. Four mozzarella cheese samples were prepared from skim cow milk, standardized at four different levels of sun flower oil (0, 1, 2 and 3%, respectively) and stored at 4±2°C for 40 days. The stored samples were examined for quality changes at 10 days interval. The total solid, fat, ash and titratable acidity increased significantly (p<0.05) with the levels of sun flower oil and storage time, while the pH values decreased throughout the storage. The protein content decreased with levels of sun flower oil and increased during storage period. The total volatile fatty acids and formal ripening index showed increasing trend as the levels of sun flower oil increased and storage time progressed. Organoleptic quality of mozzarella cheese revealed that, 2% sun flower oil secured the best acceptability (4.70), followed by 1% (4.60), 3% (4.50) and the worst score (4.00) was recorded for sample 0% sun flower oil.