In the current study, free convection heat transfer of a suspension of Nano–Encapsulated Phase Change Materials (NEPCMs) is simulated and discussed in an inclined porous cavity. The phase change materials are capsulated in nano-shells layers, while the core stores/releases large amounts of energy during melting/solidification in the vicinity of the hot/cold walls. The governing equations are introduced and transformed into non–dimensional form before being solved by using the finite element method. Simulation results are validated thoroughly. Thereafter, the consequences of the fusion temperature and the Stefan number on the distributions of streamlines, isotherms, and the heat capacity ratio, as well as the heat transfer characteristics, are analyzed for different inclination angles of the cavity. Inspection of the results demonstrates that the best heat transfer performance occurs for the non–dimensional fusion temperature of 0.5 and the inclination angle of 42°. It is found that a decrease in the Stefan number improves heat transfer. The results also show that the presence of the NEPCM particles generally leads to heat transfer improvement. •Heat transfer of nano–encapsulated phase change materials (NEPCMs) is addressed.•The porous cavity is filled with a suspension of NEPCM particles.•The finite element method is employed to solve the phase change governing equations.•The effect of fusion temperature on the thermal behaviour of the cavity is examined.•Using NEPCM particles could enhance the heat transfer up to 28%.