The objective of this paper is to investigate the energy transmission rate's features of the natural convective radiative Fe 3 O 4 - H 2 O nanofluid and Fe 3 O 4 - Cu - H 2 O hybrid nanofluid flow in a tilted square porous cavity under the influence of heat source/sink. The marker and cell method is adopted to solve the system of partial differential equations. The outcomes explore that in the existence of heat source, by augmenting the volume fraction of spherical-, cylindrical-, column-, and lamina-shaped nanoparticles from 1% to 5% in water, the average heat transfer rate is boosted by 6.07%, 8.36%, 9.89%, and 14.95%, respectively. In the existence of heat sink, the increment is noticed as 2.67%, 3.68%, 4.37%, and 6.64%, respectively. Therefore, the shape of the nanoparticles considerably varies the heat transfer rate. In the existence of heat source, by magnifying the volume fraction of spherical-, cylindrical-, column-, and lamina-shaped Fe 3 O 4 - Cu nanoparticles from 1% to 5% in water, the mean heat transfer rate is magnified by 7.23%, 11.03%, 14.15%, and 31.36%, respectively. In the existence of heat sink, the magnification is detected as 3.18%, 4.87%, 6.27%, and 14.09%, respectively. This result confirms that the proper combination of nanoparticles considerably enhances the heat transfer characteristics of base fluids. The findings of this study may be helpful for a better understanding of hydrothermal features of thermal systems such as heat exchangers, helical heat sinks, solar collectors, periodic pin-fins, mini shell and tube heat exchangers, plate evaporators, photothermal cancer treatment, and microvascular vessels using various unitary and hybrid nanofluids.