Bulk and nanoselenium (Se) seed priming has become a state-of-the-art agronomic strategy to strengthen plant defenses against environmental stressors. An important micronutrient that supports plant stress tolerance, growth and development is Se. The various ways in which Se seed priming affects important physiological and biochemical pathways are examined in this study. An increase in metabolic readiness and nutrient uptake efficiency promotes better seed germination and stronger plant establishment. Additionally, Se increases the activity of antioxidant enzymes, controls reactive oxygen species (ROS), decreases lipid peroxidation, and promotes secondary metabolite synthesis, all of which strengthen plant defenses. By increasing oxidative stress tolerance and optimizing water and nutrient usage efficiency, Se seed priming has shown great promise in reducing abiotic stresses such as heavy metal toxicity, salinity and drought. Furthermore, under biotic stress conditions, Se-primed seeds improve their resilience to pests and diseases by strengthening their biochemical and structural defense systems. However, problems such as toxicity at greater dosages, environmental hazards, and the expense of nano-Se formulations limit the effectiveness of Se. Subsequent investigations should concentrate on refining Se priming techniques via sophisticated nanoformulations, accurate dosage guidelines, and the incorporation of Se priming into environmentally friendly agricultural practices. By addressing these issues, Se seed priming will be safer and more widely used to increase the productivity of crops and their resilience to stress in the face of climate change, advancing global food security and sustainable agriculture. However, despite these advances, more investigations are still needed to determine the long-term impacts of Se nanoformulations on plant metabolic networks, soil health, and environmental sustainability. For scholars and professionals looking to use Se seed priming in agricultural techniques, this review provides a thorough foundation.