The antioxidant activity of Aspergillus fumigatus was assayed by different procedures and correlated with its extracellular total phenolic contents. Different physio-chemical parameters were optimized to enhance the activity. The culture grown under stationary conditions for 10 days at 25°C at pH 7 gave the best antioxidant activity. Statistical approaches demonstrated sucrose and NaNO(3) to be the most suitable carbon and nitrogen sources, respectively. Response surface analysis showed 5% sucrose, 0.05% NaNO(3), and incubation temperature of 35°C to be the optimal conditions for best expression of antioxidant activity. Under these conditions, the antioxidant potential assayed through different procedures was 89.8%, 70.1%, and 70.2% scavenging effect for DPPH radical, ferrous ion and nitric oxide ion, respectively. The reducing power showed an absorbance of 1.0 and FRAP assay revealed the activity of 60.5%. Extracellular total phenolic content and antioxidant activity as assayed by different procedures positively correlated.