In this work, we carried out a numerical study of the thermal Rayleigh effect on natural double-diffusive convection in a non-Newtonian fluid obeying the Carreau-Yasuda rheological model, confined in a square cavity whose horizontal walls are adiabatic, while the vertical walls exhibit uniform temperatures and concentrations. The approach adopted is based on the finite volume method, enabling the complete conservation equations to be solved. The main parameters studied are the thermal Rayleigh number (10 ≤ RaT ≤ 106), the power index (0.4 ≤ n ≤ 1), the Pearson number (0 ≤ m ≤ 3), the time constant (0 ≤ λ ≤ 10) and the ratio between viscosities at the extreme shear limits (0 ≤ s ≤ 1). The results reveal that increasing the thermal Rayleigh number (RaT) and Pearson number (m), which models the thermo-dependent effect, leads to a significant improvement in heat transfer rate (Nu) and mass transfer rate (Sh). Furthermore, a decrease in the parameters n and s induces an intensification of exchanges, reflecting a pseudo-plastic behavior favorable to convection. Increasing the time constant λ also favors heat and mass transfer by reducing apparent viscosity. This study highlights the predominant influence of rheological and thermo-dependent parameters on double-diffusive convection mechanisms.