Biodiesel as an alternative diesel fuel prepared from vegetable oils or animal fats has attracted more and more attention because of its renewable and environmental friendly nature. Many recent studies shows that 20% proportion of biodiesel-diesel blend (B20) can substantially reduce the hydrocarbon (HC), carbon monoxide (CO) and smoke emissions. However, there is a slight increase in NOx emission for B20 than that of diesel and it was a barrier to market expansion. The addition of antioxidant additives was the most effective method to mitigate the NOx emission. Hence, in this paper experimental investigation has been carried out to mitigate the NOx emission in Annona biodiesel (A20) operated diesel by addition of antioxidant additives. The antioxidant additives such as p-phenylenediamine, A-tocopherol acetate and L-ascorbic acid were used in the present investigation. In recent years Annona biodiesel has been considered as potential novel renewable energy source in India. Therefore in this experimental investigation was conducted to improve the A20 (7) (20% of annona methyl ester with 80% of diesel) with the help of antioxidant additives. It was evidently proved from the experimental investigation that use of antioxidant additive was effective in controlling the NOx emission in diesel engine. Result shows that 250mg concentration of p-phenylenediamine additive with A20 blend was optimum for NOx mitigation up to 25.7% when compared to that of diesel without any major modification.