Phytochemicals are secondary metabolites synthesized by plants to provide assistance in survival and protection from environmental stress factors. Many phytochemicals have anti-oxidative and anti-inflammatory characteristics that improve health and prevent diseases, such as cancer, diabetes, cardiovascular disease, and neurodegenerative disorders, in animals. In addition to the health-improving and disease-preventing effects, phytochemicals also have been shown to retard the aging process and extend lifespans in various experimental animal studies using yeast, worms, flies, fishes, and rodents. In this chapter, we review the longevity benefits and putative underlying mechanisms of phytochemicals, including resveratrol, curcumin, quercetin, and catechin.