Objective: The present investigation includes the preliminary screening of phytochemicals and evaluation of in vitro antidiabetic activity of Psidium guajava leaves extracts. Materials and Methods: Plant material was subjected to the extraction preparation by soxhlet apparatus by using various solvents such as aqueous, ethanol, chloroform, petroleum ether and hexane. The various kinds of phytochemicals were detected and then in vitro antidiabetic activity of P. guajava were detected by using alpha amylase and alpha glucosidase enzyme in an in vitro model. Results: The study reveals the presence of phytochemicals such as carbohydrate, tannin, flavonoids, phenols etc., Among the various extracts the aqueous and ethanolic extracts which contains the large number of phytoconstituents. The P. guajava leaves has been successfully inhibited both the enzymes in an in vitro model. The aqueous extracts of P. guajava leaves inhibited the alpha amylase and alpha glucosidase enzymes as 72.1% and 74.8% respectively. The ethanolic extract of P. guajava leaves inhibited the alpha amylase and alpha glucosidase enzymes as 97.5% and 91.8% respectively. Conclusion: From the results obtained in the current studies, the P. guajava leaves have a prominent antidiabetic property in an in vitro model and further studies can be carried out in an in vivo model and the isolation of activie compound from P. guajava leaves extract is needed.