A numerical investigation is performed into the heat transfer performance and entropy generation characteristics of a mixed convection magnetohydrodynamic (MHD) flow of Al2O3-water nanofluid in a vertical asymmetrically-heated parallel-plate channel subject to viscous dissipation effects. In performing the analysis, the effects of the Lorentz force and Joule heating are modeled using the transverse momentum balance equation and energy balance equation, respectively. Moreover, the Hartmann number is assigned a value of Hm = 0 (no magnetic field) or Hm = 2 (weak magnetic field). The results show that the presence of the magnetic field increases the local Nusselt number at the hot wall. Moreover, the enhancement in the heat transfer performance increases with an increasing nanoparticle concentration. The local Nusselt number at the cold wall also increases with an increasing nanoparticle concentration. However, for a constant particle concentration, the Nusselt number reduces given the application of a magnetic field. Finally, the average entropy generation number also reduces when a magnetic field is applied. (C) 2015 Elsevier Ltd. All rights reserved.