An extracellular α-glucosidase produced by Aspergillus niveus was purified using DEAE-Fractogel ion-exchange chromatography and Sephacryl S-200 gel filtration. The purified protein migrated as a single band in 5% PAGE and 10% SDS–PAGE. The enzyme presented 29% of glycosylation, an isoelectric point of 6.8 and a molecular weight of 56 and 52 kDa as estimated by SDS-PAGE and Bio-Sil-Sec-400 gel filtration column, respectively. The enzyme showed typical α-glucosidase activity, hydrolyzing p-nitrophenyl α-d-glucopyranoside and presented an optimum temperature and pH of 65°C and 6.0, respectively. In the absence of substrate the purified α-glucosidase was stable for 60 min at 60°C, presenting t 50 of 90 min at 65°C. Hydrolysis of polysaccharide substrates by α-glucosidase decreased in the order of glycogen, amylose, starch and amylopectin. Among malto-oligosaccharides the enzyme preferentially hydrolyzed malto-oligosaccharide (G10), maltopentaose, maltotetraose, maltotriose and maltose. Isomaltose, trehalose and β-ciclodextrin were poor substrates, and sucrose and α-ciclodextrin were not hydrolyzed. After 2 h incubation, the products of starch hydrolysis measured by HPLC and thin layer chromatography showed only glucose. Mass spectrometry of tryptic peptides revealed peptide sequences similar to glucan 1,4-alpha-glucosidases from Aspergillus fumigatus, and Hypocrea jecorina. Analysis of the circular dichroism spectrum predicted an α-helical content of 31% and a β-sheet content of 16%, which is in agreement with values derived from analysis of the crystal structure of the H. jecorina enzyme.