We investigate the effect of an external magnetic field on the heat and mass transport in double diffusive convection in a viscoelastic fluid layer. The Oldroyd-B constitutive equation is used to model viscoelasticity. Nonlinear stability analysis is carried out using a minimal representation of a Fourier series consisting of two terms. A novel transformation due to Siddheshwar et al. [25] is used in the momentum equation in deriving the non-autonomous generalized Lorenz model. The generalized Lorenz system has been solved numerically using the Runge-Kutta-Fehlberg (RKF45) method to quantify the heat and mass transport. It is established that the applied magnetic field has a stabilizing effect, hence reducing heat and mass transport. (C) 2013 Elsevier Ltd. All rights reserved.