This research comprehensively analyzes the role of magnetic fields in convective heat transport in pentagonal thermal annuli by placing a concentric heated pentagon of unit perimeter length. The study investigates the effect of magnetic fields on nanofluid-based natural and mixed convection. Numerical simulations with appropriate validations are performed to analyze the thermal performance. The Rayleigh number (Ra), Hartmann number (Ha), and Reynolds number (Re) are employed to evaluate the thermal characteristics, specifically focusing on the average Nusselt number (Nu). The study maintains consistent working fluid volumes, heating, and cooling surfaces across all pentagonal configurations. The results indicate that convective heat transfer improves with an increasing Ra and Re. However, the increasing Ha decreases Nu for the natural convection system but significantly enhances Nu for the mixed convection system. Due to the high cooling effect of jet action, the average Nusselt number (Nu) receives the most boost at the maximum Re, with an improvement of up to 38.96%. In general, a mixed convection flow regime is always advantageous compared to natural convection and heat transfer enhancement goes up to 37.25% compared to natural convection. The findings from this study have practical implications for optimizing and designing pentagonal thermal systems in various applications where magnetic fields can be employed to enhance thermal convection (such as material processing, chemical mixing, heat exchangers, biomedical devices, and others).