The aim of this work was the evaluation of physiological behavior of Aspergillus flavus affected by the application of sub-lethal doses of microencapsulated 2(3)-tert-butyl-4 hydroxyanisole (BHA). For this, peanut meal extract agar (PMEA) and peanut kernels with modified water activity (aw) (0.96 and 0.99) and a sub-lethal dose (0.6 mM) of an BHA formulation was used. Fungal physiological aspects as growth rate, time to growth and AFB1 evolution were modified by the formulation, especially on PMEA at both aw. In general, conidial and vesicle size of the mold only were affected by growth substrate, being higher on sterile seed than on PMEA regardless of aw condition. However, positive correlation (p<0.05) observed in controls between radius and biomass responses was altered by the application of the formulation, mainly under the lowest aw in both substrate evaluated. Finally, presence of encapsulated antioxidant showed significant change in Pearson coefficients respect to the controls for all studied parameters. As conclusion, sub-lethal doses of formulation lead in reduction on growth and toxin accumulation, but conidial and vesicle size were not affected. Results of this work indicate the need to consider both fungal primary and secondary metabolism to determine the effect of food grade antioxidant formulation.