To compare the effects of crude extract from Antidesma acidum, bioflavonoid and α-tocopherol on oxidative stress in cats with naturally occurring CKD. Thirty-four cats presented to the Small Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University were studied. They were assigned into four groups: the clinically normal (n = 16) and the CKD cats (n = 18) with increase level of creatinine concentrations (2.8-5.0 mg/dl) and blood urea nitrogen (BUN) (>35 mg/dl). The CKD cats were randomly divided into three subgroups including cats received Antidesma acidum 120 mg/kg orally once a day (n = 6), bioflavonoid 10 mg/cat orally once a day (n = 5) and α-tocopherol 800 IU/cat orally once a day (n = 7). Blood collection were performed to measure complete blood count, blood chemistry and the assays of oxidative stress parameter including glutathione (GSH), oxidized glutathione (GSSG) and glutathione peroxidase (GPx) on day 0 for the clinically normal cats and on day 0, 14, 28, 42, 56 for the CKD cats. The cats with CKD had significantly increased levels of oxidative stress parameter in plasma than the clinically normal cats. The crude extract from Antidesma acidum had significantly decreased the creatinine levels and increased GPx levels in cats with CKD on day 56, but increased GSSG levels more than oral bioflavonoid and α-tocopherol on day 42. Whereas the bioflavonoid had significantly increased GSH/GSSG ratio on day 14 and did not decrease creatinine levels. Further research is needed to study the exact mechanism of how Antidesma acidum decreased creatinine levels in the CKD cats.