The present study scrutinizes the significance of Joule heating, Soret, and Dufour effects on the mixed convective flow of the Williamson fluid over a non-linear curved stretching sheet. The governing highly non-linear coupled partial differential equations (PDEs) are transformed into non-linear coupled ordinary differential equations (ODEs). The resulting set of ODEs is converted into the system of first-order ODEs and solved numerically by adopting finite difference-based built-in MATLAB code bvp4c. The effect of various physical parameters, i.e. thermal buoyancy force and mass buoyancy force parameters, Prandtl number, Schmidt number, magnetic field parameter, non-linear stretching parameter, curvature parameter, Porosity parameter, Soret, and Dufour number, and the Brickman number on velocity, pressure, temperature, and concentration profiles are shown through tables and graphs. It is seen that by upsurging, the Soret number temperature decreases and concentration profile increases, whereas reverse relation is seen for the Dufour number.