This work examines the steady double-diffusive mixed convection flow in a porous open cavity filled with a nanofluid using mathematical nanofluid model proposed by Buongiorno. The analysis uses a two-dimensional square cavity of size with an inlet of size in the bottom part of the left vertical wall and an outlet of the same size in the upper part of the right vertical wall. The mathematical problem is represented by non-dimensional governing equations along with the corresponding boundary conditions, which are solved numerically using a second-order accurate finite difference method. The developed algorithm has been validated by direct comparisons with previously published papers, and the results have been found to be in good agreement. Particular efforts have been focused on the effects of the key parameters on the fluid flow, heat and mass transfer characteristics. In addition, numerical results for the average Nusselt and Sherwood numbers are presented in tabular forms for various parametric conditions and discussed.