A Multigrid approach was employed to examine the fluid flow and heat transfer features of a nano-fluid undergoing mixed convection within a vented enclosure featuring a variety of iso-perimetric-shaped obstacles. Concerning the cavity, the inlet port is situated at the lower left corner, while the outlet port is located at the upper right corner. The study involved conducting simulations with a range of control parameters by employing the higher-order mixed finite element technique. To capture key physical processes like mass transfer, fluid flow, and heat transfer within the model, we employed a numerical technique called finite element discretization. Specifically, we used a stable combination of cubic and quadratic (P3 ∕P2) approximations on a hybrid grid to discretize the governing equations, ensuring accurate and reliable results. The study examines the influence of governing parameters within specified ranges, including nanoparticle volume fraction (0 % ≤ φ ≤ 10 %), the Richardson number (0.01 ≤ Ri ≤ 5), and obstacle positions (0.3 ≤ C ≤ 0.7). Adding more nanoparticles to a liquid makes it better at conducting heat, which helps the liquid transfer heat more efficiently. The findings indicate that, in all instances, isothermal obstacles lead to a more significant increase in the average Nusselt number compared to adiabatic obstacles.