Objective: To assess the putative diuretic and antioxidant properties of Cassia occidentalis (C. occidentalis) leaves' aqueous extract. Methods: Adult rats were administered with C. occidentalis leaves aqueous extract acutely (24 h) and subchronically (7 d), at doses 80, 160, 240, 320, and 400 mg/kg (per os). Negative control group received only an equivalent volume of distilled water, while the two positive control groups received the diuretic drugs furosemide (20 mg/kg, ip.) and hydrochlorothiazide (HCTZ) (20 mg/kg, ip.). Urinary elimination of electrolytes in response to treatments was evaluated, together with changes in concentrations of creatinine, urea, aldosterone, glucose, and albumin in urine and plasma. Various urinary indicators of kidney function and plasmatic markers of oxidative stress were also assessed. Results: The acute administration of C. occidentalis increased the urinary excretion of 107.58% at the higher dose tested, compared to negative control. The reference drugs furosemide and HCTZ induced increases of 84.27% and 48.05%, respectively. Acutely, the extract induced Na