Senna obtusifolia (Fabaceae; Synonyms: Cassia obtusifolia, Cassia humilis) is a plant widely found in the state of Amapá, popularly known as “Mata-pasto”, it is widely used worldwide, being used in local and traditional medicine, for diseases related to rheumatism, headache, hepatitis and diuretic. The research was carried out using the databases of theses, dissertations and indexed articles. Additional information was collected from books, reviews and related documents. The morphometric study of the leaves of S. obtusifolia was found in the literature. The analyzes revealed different morphological and anatomical patterns, which are important on the adaxial and abaxial surfaces, since the surface is glabrous and has calcium oxalate druses, unicellular trichomes, epidermal idioblasts. The study of morphology is important in the medicinal activity of the plant since the secondary metabolites in plants are affected by different biotic and abiotic stresses. Thus, stress conditions affect secondary metabolites or the so-called active ingredients and other compounds that plants produce, which are generally the basis of their medicinal activity. According to the literature, several classes of secondary metabolites were found, such as anthraquinones, flavonoids, terpenoids and others in the leaves of S. obtusifolia. Current evidence indicates that the secondary metabolites it contains in extracts of S. obtusifolia have hypocholesterolemic, antioxidant, allelopathic, antinociceptive, anti-inflammatory, cancer-preventing, arthritis, diabetes, heart disease, kidney and liver toxicity, and urinary tract infections. Detailed information in the literature on S. obtusifolia reveals that this species has a wide pharmacological use proven in scientific research.