This work examines the mixed thermal convection of copper oxide-water nanofluid through a grooved cavity channel with a central conducting block. As boundary conditions of the chamber, the left, right, and the top walls are taken to be adiabatic while the bottom wall is subjected to a higher temperature. The nanofluid enters into the grooved channel cavity through a port at the top left side and exits from another opening at the top right side. The conducting cylinder is placed centrally in the grooved cavity. An external magnetic field is imposed horizontally. Due to the presence of grooved shape and conducting block in the cavity, thermo-fluid phenomena alter significantly depending on the involved flow controlling variables like Reynolds number (Re = 10 − 200), Hartmann number (Ha = 0 − 70), Richardson number (Ri = 0.1 − 100). The non-dimensionless transport equations are numerically solved following the finite element technique. The obtained results are depicted through temperature distributions and streamline patterns for the various combinations of thermal governing parameters. It is revealed that, as Re increases, the heat transfer increases for all values of Ri. Increased intensity of the applied magnetic field reduces the thermal energy transport.