A finite element analysis is performed on the conjugated effect of joule heating and magneto-hydrodynamic on double-diffusive mixed convection in a horizontal channel with an open cavity. Homogeneous flows are imposed throughout the channel. Consistent high temperatures and concentrations are imposed at the bottom wall of the cavity. The other sides of the cavity along with the channel walls are considered as adiabatic. The effects of the various parameters (Richardson number, Hartmann number, joule heating, buoyancy ratio and Lewis number) on the contours of streamline, temperature, concentration and density have been depicted. Moreover, the average Nusselt and Sherwood numbers as well as bulk temperature is presented for the aforementioned parameters. The results show that the aforesaid parameters have noticeable effect on the flow pattern and heat and mass transfer. (C) 2011 Elsevier Ltd. All rights reserved.