Accepted: 15 February 2021 The involvement of non-linear convection effects in a natural convective fluid flow and heat transfer along with the effects of magnetic field in a porous cavity is studied numerically. Cu-water filled cavity of higher temperature at the left wall and lower temperature at the right wall. The governing equations are organized to achieve the required flow by using two-dimensional equations of energy, continuity and momentum. Vorticity-stream function based dimensionless equations are solved using the finite difference techniques. The results are discussed for various dimensionless parameters such as the Darcy number, non-linear convection parameter, Hartmann number, Rayleigh number and solid volume fraction of the nanoparticles. An augment in streamline velocity and convection heat transfer are observed by increasing the Rayleigh number, non-linear convection parameter and Darcy number. The non-linear convection parameter has a lesser effect on the lower Rayleigh numbers. Diminished streamline intensity and reduction in convection heat transfer are noted for an increase in the strength of the applied magnetic field irrespective of the non-linear convection parameter.