Abstract: Seagrass beds support important ecosystem services, such as sediment stabilization, water quality improvement and carbon sequestration. In recent years, seagrass beds have declined worldwide. Considering eutrophication and global warming, we summarized the effects of nutrient enrichment and global warming on seagrasses. In oligotrophic environments, nitrate and ammonium can promote seagrass growth. Nitrate enrichment can disturb carbon balance of seagrass tissues, therefore negatively impacting seagrasses because nitrate needs to be reduced into nitrite, and then transformed into amino acid by a series of metabolism processes. Higher concentration ammonium can induce seagrass decline due to its toxicity. Organic nitrogen, as selectable nitrogen source of seagrasses, is effectively complementary nitrogen for seagrass. Temperature, as one of the important variables, controls seagrasses distribution and growth. Modest nutrient enrichment can increase seagrass production in spring, but higher temperature and nutrient enrichment can inhibit seagrass growth in summer. Nutrient enrichment and higher temperature in summer also accelerate macroalgae blooms, resulting in light attenuation and shift from seagrasses to macroalgae ecosystems. Further directions of research on seagrasses should include seagrass bed observation in a long term, effects of organic nitrogen on seagrasses, combined effects of nutrient enrichment and increasing temperature on seagrasses, and responses of tropical seagrass respiration to global warming.