An investigation was undertaken to analyze the effect of four different metal nanoparticles (ZnO, SiO2, Fe2O3 and MgO) on the growth of mung bean (Vigna radiata L.) plants. Agar overlay method using seedling nutrient medium containing 50 and 100 mg l−1 of each of the nanoparticles (NPs) was used for the study undertaken for 28 days. A concentration-dependent increase in fresh weight and carotenoid concentration was recorded in MgO NPs. ZnO NPs showed the highest enhancement in leaf peroxidase activity over control. Heavy metal analysis by ICP-MS of seedlings at both concentrations of NPs for 28 days showed a twofold increase at the higher concentrations with ZnO and Fe2O3 NPs. Visual and SEM observations of the MgO NP-treated roots revealed an increase in density and fibrosity, with unique globular structures on the surface of the roots. MgO nanoparticles–mung bean interaction can be a model system for investigating beneficial interactions of nanoparticles with plants.