In this investigation, we intend to present the influence of the prominent Soret effect on mixed convection heat and mass transfer in the boundary layer region of a semi-infinite vertical flat plate in a nanofluid under the convective boundary conditions. The transformed boundary layer ordinary differential equations are solved numerically using the implicit iterative finite difference method. Consideration of the nanofluid and the convective boundary conditions enhanced the number of non-dimensional parameters considerably thereby increasing the complexity of the present problem. A wide range of parameter values is chosen to bring out the effect of Soret parameter on the mixed convection process with the convective boundary condition. The effect of mixed convection, Soret and Biot parameters on the flow, heat and mass transfer coefficients is analyzed. The numerical results obtained for the velocity, temperature, volume fraction, and concentration profiles, as well as the local skin-friction coefficient, local wall temperature, local nanoparticle concentration and local wall concentration reveal interesting phenomenon, some of these qualitative results are presented through plots and tables.