Selenium (Se) is an essential mineral for plant development, tolerance to environmental stress, and human and animal nutrition. In agriculture, under climate change conditions, selenium use has been shown to be an effective technique of improving crop tolerance to environmental stresses such as drought, salt, and high temperatures. Selenium fertilizers boost antioxidant defenses, improve nutrient use efficiency, and increase crop output and quality. In addition to this, selenium is also applied in biofortification, which rectifies nutritional deficiency in humans and animals. Although useful, the use of selenium in agriculture is challenging in terms of risks of toxicity hazards, environmental pollution, and selenium interactions with soil microbiota influencing nutrient cycling. Mobilization of selenium in water and soil requires site-specific practice to avoid harmful effects. Development of precision agriculture, nano-fertilizers, and genetic enhancement of selenium-efficient plants provides environmentally friendly strategies for optimization of selenium use with minimized risk. When used in combination with climate-resilient agriculture practices, including organic amendments, microbial inoculants, and conservation agriculture, it can be made more effective. Additionally, policy and regulatory frameworks must be developed to promote responsible and effective use of selenium in agriculture. This chapter discusses the function of selenium in sustainable agriculture in the context of climate change, its advantages, limitations, and directions for future research to improve soil health, crop yields, and global food security.