Coumarins are natural products characterized as 1,2 benzopyrones widely distributed in plants, as well as, in many species of fungi and bacteria. Nowadays, many synthetic procedures allow the discovery of coumarins with expanded chemical space. The ability to exert noncovalent interactions with many enzymes and receptors in live organisms lead the coumarins to exhibit a wide range of biological activities and applications. Then, this manuscript provides an overview of the use of coumarins compounds in medicinal chemistry in treating many diseases. Important examples of the last years have been selected concerning the activities of coumarins as anticoagulant, anticancer, antioxidant, antiviral, anti-diabetics, anti-inflammatory, antibacterial, antifungal and anti-neurodegerative agents. Additionally, it also includes applications of coumarins as fluorescent sensors for biological systems. Thus, this work aims to contribute to the development of new rational research projects for the treatment and diagnosis of pathologies using coumarin derivatives.