Diuretics are drugs widely used in the therapy of several diseases. However, many synthetic diuretics are associated with adverse effects. Caesalpinia bahamensis Lam., known as “brasilete”, is a medicinal plant utilized by the Cuban people to treat kidney diseases, but there is a lack of toxicological and pharmacological studies that support its traditional use. This research aimed to evaluate the diuretic activity and acute oral toxicity of the aqueous and hydroalcoholic extracts of the stems of Caesalpinia bahamensis. With regard to the diuretic activity, thirty Wistar rats were used and divided into five groups, receiving the following treatments by intragastric gavage: sodium chloride 0.9% (negative control), furosemide 20 mg/kg (positive control), hydrochlorothiazide 10 mg/kg (positive control), aqueous extract (10, 100, and 200 mg/kg) and hydroalcoholic extract (10, 100 and 200 mg/kg). The urine volume was measured every hour for four hours. The urinary flow was calculated and the urinary concentration of potassium and sodium was determined by flame photometry. The acute oral toxicity was evaluated by the class method and classified according to the Globally Harmonized System (GHS). The urinary flow and the natriuretic and kaliuretic activity were increased in the groups, which received the aqueous extract (200 mg/kg) and the hydroalcoholic extract (200 mg/kg), comparable to hydrochlorothiazide. The highest diuresis was observed at two hours after the administration. In addition, the extracts showed no sign of toxicity at a single dose of 2000 mg/kg. They were classified in category 4 according to GHS. The results obtained in this study support the traditional use of aqueous and hydroalcoholic extracts of Caesalpinia bahamensis and represent a contribution to the scientific knowledge about this plant species with regard to its potential future clinical use as a phytodiuretic drug.