Melanins, a black-brown pigment formed from phenolic precursors, are multifuncional compounds found in diverse fungal species. This pigment has been reported to act as "fungal armor" because protect these microorganisms against harmful environmental conditions. Structure of the melanins presents some semiquinone radicals, which render for the polymer a potential free radical scavenger, photon absorption and cation binding. These properties determine the antioxidant, antiradiation and antitoxic activity of melanins. In present work, we investigated the free radical scavenging and metal chelating activity of the melanin extracted of the culture medium after growth of the Aspergillus nidulans mutant presenting overproduction of this pigment. The radical scavenger activity was evaluated by reduction of 1,1-diphenyl-2-picryl-hydrazyl  (DPPH) alcoholic solution in the presence of a hydrogen-donating antioxidant. The chelating activity was determined by  (Fe²⁺) ferrous metal ions chelating propriety and was quantified by decrease in the red color of the Ferrozine-Fe²⁺ complex. Our results showed that melanin pigment in concentration above of 50 μg/mL was able to reduce the stable radical DPPH in about of 90%. This inhibition percentage was similar to Trolox (used as reference antioxidant) and synthetic melanin. As regards the metal chelating activity, the results showed that A. nidulans and synthetic melanins reduced the formation of Ferrozine-Fe²⁺ complex proportionally to increase of pigment concentration.  In addition, these melanins exhibited 90% chelation of ferrous ion at 100 μg/mL while EDTA (used as standard metal chelator), in the same concentration, presented only 45% metal chelating capacity. Then, these analyses suggest that the melanin pigment extracted from A. nidulans has antiradical activity, neutralizing free radicals and also is a metal chelating agent reducing the redox potential of the Fe²⁺ ion, that is the most powerful pro-oxidant among the various species of metal ions.