The triple-diffusive flow, heat and mass transfer in a cavity filled with a porous medium and saturated with a mixture is theoretically studied in a cavity with differential temperature and concentrations at the side walls. The effect of buoyancy forces due to mass transfer of phases is also taken into account using the Boussinesq approximation. The governing equations are transformed into a non-dimensional form and numerically solved using the finite element method. Five groups of non-dimensional parameters including the Rayleigh number, the Lewis numbers for phases 1 and 2, and the buoyancy ratio parameters for phases 1 and 2 are obtained. The effect of each group of non-dimensional parameters on the heat and mass transfer in the cavity is discussed. The results show that for specific values of the Lewis number of one phase, the heat transfer of the mixture and the mass transfer of the other phase can be maximum. The presence of one phase could reduce or enhance the mass transfer of the second phase depending on the Lewis number of phases.