The creation of new bioactive compounds derived from ethno-medicine is becoming increasingly popular. Historically, different parts of guava (Psidium guajava Linn.) are used to treat a wide range of diseases. Extensive in vitro and in vivo pharmacological research has demonstrated the potential of leaf extracts for the co-treatment of numerous high-prevalence diseases, supporting the use of traditional medicine in the treatment of conditions such as diabetes, cardiovascular disease, cancer, and parasitic infections. Additionally, the bioactive composition of the leaves and several phytochemical subclasses and compounds have been linked to the biological activity of the plant. The phenolic compounds in guava leaf are associated with glucose regulation. An attempt has been made with an objective to compile and enlist the information from in vitro and in vivo studies reported on guava leaves over the past decade in order to inform future research into the findings of bioactive components.