Acylase I from Aspergillus melleus (AMA) displayed catalytic promiscuity towards one-pot asymmetric Mannich reaction in acetonitrile for the first time. AMA showed favourable catalytic activity with good adaptability to different substrates. The activity and stereoselectivity of the enzyme could be improved by adjusting solvent, pH, water content, temperature, molar ratio of substrates and enzyme loading. The enantioselectivities up to 89% ee, diastereoselectivities up to 90:10 dr (syn/anti) and yields up to 82% were achieved. This work offered a novel case of enzyme catalytic promiscuity and a potential synthetic method for organic chemistry. (C) 2014 Elsevier B.V. All rights reserved.