The incredible health benefits of naturally occurring fruits and vegetables are a boon to human beings. The diverse array of phytonutrients in these natural products is capable of exhibiting tremendous health promoting activities. Guava (Psidium guajava) is well known for its medicinal properties due to its phenolic, flavonoid, carotenoid, andterpenoid compounds. The fruit, leaf, stem, and bark of this berry fruit has been used from ancient days for various ailments. Scientific investigations report a plethora of evidence supporting its antioxidant, antimicrobial, anti-diarrheal, antihelminthic, andantispasmodic effects. Moreover, its potential to treat diabetes, cardiovascular diseases,gastroenteritis, hepatotoxicity, and dental decay were substantiated by various in vitro and in vivo assays. The anti-allergic, anti-inflammatory, and antinociceptive activities and dermoprotective effects of phytocomponents in guava were also reported experimentally.The astounding health benefits and the mechanism of action of guava phytonutrients is summarized in this chapter.