Psidium guajava (guava, peru or amarood in Indian common language) is well known tropic tree which is abundantly grown for fruit. Psidium guajava is a shrub or small tree usually growing 1-6 m tall, but occasionally reaching 10 m in height. Guava or amarood is a member of the Myrtaceae family. The genus Psidium includes about 150 species, but Psidium guajava is the most important fruit of this genus. Guava is believed to have originated from an area extending from southern Mexico into or through Central America. The Spaniards and Portuguese are considered to be responsible for distribution of guava fruit to other parts of the world. Many countries have a long history of using guava for medicinal purposes. This plant finds applications for the treatment of diarrhea, dysentery, gastroenteritis, hypertension, diabetes, dental caries and pain relief and for improvement in locomotors coordination. Guava leaf extract is being used as a medicine in cough, diarrhea, and oral ulcers and in some swollen gums wound. The Polyphenolic compounds in guava help to cure cancerous cells and prevent skin aging before time. The presence of terpenes, caryophyllene oxide and p-selinene in Guava produces relaxation effects. Guava leaves contain many compounds which act as fungistatic and bacteriostatic agents. Guava has a high content of important antioxidants and has radio-protective ability. Quercetin is considered as most active antioxidant in the guava leaves and is responsible for its spasmolytic activity. Guava possesses anti-viral, anti-inflammatory, anti-plaque and anti-mutagenic activities. Guava extract shows antinociceptive activity and is also effective in liver damage inflammation and serum production. Guava leaves have high antibacterial activity in extracts that can inhibit the growth of bacteria’s. Terpinene and pinene are present into the aqueous extract of plant’s leaves which shows antimicrobial activity. Guava leaves have quercetin-3-arabinoside and quercetin which is found useful in controlling intestinal spasm in diarrhoea. Quercetin repressed intestinal contraction encouraged by enhanced absorption of calcium. Quercetin has a strong effect on ileum. It is thought that quercetin in guava leaf are responsible for its spasmolytic activity. Quercetin has free radical balancing activity, which helps as an antioxidant and aids in wound healing.