Exercise has been overlooked as a potential therapy in chronic kidney disease (CKD), mainly due to a lack of understanding on its safety aspects. Notably, there is no data on renal function after exercise in CKD considering its stages. We investigated the acute effects of a 30-minute moderate-intensity aerobic exercise bout on glomerular filtration rate (GFR) and albuminuria in twenty-two non-dialysis CKD patients divided into: CKD stages 1 and 2 (CKD1-2) and; CKD stages 3 and 4 (CKD3-4). Eleven body mass index-, age-, and sex-matched healthy individuals served as control (CON). Blood and urine samples were collected before, immediately after, and up to 90 minutes post exercise for creatinine and albumin assessments. GFR was determined by creatinine clearance (GFRCr-Cl). All CKD patients had significantly lower peak oxygen uptake than CON. CKD1-2 and CKD3-4 had increasingly higher serum creatinine than CON (9.6±2.6 mg/L; 25.6±1.01 mg/L; 7.5±1.4 mg/L, respectively); however, no within-group changes in serum or urinary creatinine were observed across time. GFRCr-Cl was decreased in CKD1-2 and CKD3-4 when compared with CON (91±17 ml/min-1/1.73m2-1; 34±15 ml/min-1/1.73m2-1; 122±20 ml/min-1/1.73m2-1, respectively). Most importantly, exercise did not affect GFRCr-Cl in none of the groups across time. Albuminuria was significantly higher in CKD3-4 (297±284 µg/min-1) than in CON (5.4±1.4 µg/min-1), but no within-group changes were observed after exercise. In conclusion, a single 30-minute moderate-intensity aerobic exercise bout does not impair renal function in non-dialysis CKD patients, regardless of disease stage, supporting the notion that exercise training can be safe in this disease.