Environmental stress factors including abiotic stresses (heavy metals, drought, and salinity etc.) or biotic pathogens (bacteria, fungi, and nematodes etc.) contribute to major losses to global crop yields and cause food security threats, resulting in economic losses. Improving crop yield under these environmental constraints is critical to assure the food supply and sustainable agriculture. The advancement in nanotechnology has tremendously solved these global issues. Magnesium oxide nanoparticles (MgONPs) is a non-toxic, eco-friendly, highly stable material that has wider opportunities for its production at nanoscale. Differently synthesized (physical, chemical and biological) MgONPs have been found to induce the plant resistance against these stresses through a combination of physiochemical and molecular pathways that strengthen the structural barriers, improve nutrients availability, osmoregulation, photosynthetic efficiency, hormonal regulation, activate antioxidant defense systems and induce stress-responsive genes. These defense mechanisms help plant adaptation to environmental stressors. Furthermore, MgONPs act as antibacterial, antifungal or nematicidal agent that inhibits the growth of pathogens, reduces pathogen colonization, thereby reduces the disease incidence and protects plant against biotic stresses. In this review, we have discussed the multifaceted mechanisms of MgONPs in managing the abiotic and biotic stresses, thereby imparts plant protection against environmental stresses. In addition, knowledge gaps along with research questions and future recommendations have been delineated in this review.