This article focuses on thermosolutal natural convection in an inclined rectangular enclosure filled with copper nanoparticles suspended in a binary base fluid with the Soret effect. The longer walls have constant temperatures and concentrations, while the short ones are assumed to be adiabatic and impermeable except in the left lower region, we apply a constant temperature. The finite volume method is used to solve the governing equations. The effects of varying the numbers of Soret, Lewis, Prandtl, and Rayleigh, inclination angle of the cavity, nanoparticle volume fraction, and aspect ratio of the cavity on heat and mass transfer are analyzed. We also examined the distribution of concentration, temperature, and vorticity on the left side wall of the cavity. Results show that the mass transfer increases with rising Soret number and cavity aspect ratio, and that Prandtl and Lewis numbers, and nanoparticle volume fraction play a significant role in enhancing heat transfer.