Due to their unique redox properties and high surface reactivity, cerium oxide nanoparticles (NPs) have emerged as promising nanomaterials in the improvement of plant resilience against environmental stresses. This chapter reviews the dual role of cerium oxide nanoparticles (CeO2 NPs) in the mitigation of abiotic and biotic stresses in plants. Under abiotic stress conditions, such as heavy metal toxicity, salinity, drought and temperature extremes, CeO2 NPs act as powerful antioxidants due to their reversible Ce3+/Ce4+ redox cycle and efficiently scavenge reactive oxygen species (ROS), maintaining cellular redox homeostasis. They facilitate the immobilization, adsorption, and chelation of toxic metals such as Cd, Pb and As, reducing their bioavailability and translocation to aerial tissues. Besides this, CeO2 NPs enhance photosynthetic efficiency, stabilize chlorophyll pigments, and improve nutrient uptake and water balance under stressful environments. A better understanding of these interactions would provide insight not only into plant-nanoparticle associations but also open up new ways for sustainable agricultural applications in nanotechnology regarding stress management and crop improvement.