Researches have shown that marolo (Annona crassiflora Mart.) contains many biologically active phytochemical classes with antidiabetic properties. Therefore, in order to obtain scientific data that contribute to a better insight of the species, integrating both safety and efficacy to the practice of using the plant as medicine, the study of A. crassiflora Mart. leaves was chosen. To evaluate the possible effect of A. crassiflora Mart. in diabetic rats, blood glucose levels, concentrations of fructosamine, urea, creatinine, ASL and ALT was determined in serum samples from animals treated with 300 mg of hydroethanolic extract 70% (v/v) per kg of animal weight. Glucose levels were determined by Trinder reaction. Dosages of urea and creatinine were held using the Jaffé method for creatinine and the enzyme method colorimetric for urea in automated apparatus (HumaStar 80, Brazil/Alfenas). The concentration of fructosamine was measured by a commercial kit kinetic method (analyzes ®) and the reading was held in Bioplus® (Brazil-Alfenas). Based on the results obtained in this study, it can be concluded that administrating the extract, according to the adopted protocol, did not change the biochemical parameters that were analyzed in the normal and diabetic rats' serums.