The aim of this study was to evaluate the safety of Chlorella vulgaris CK-22 as a food supplement. We examined mutagenicity, acute toxicity and subacute toxicity using Wistar rats administered Chlorella powder (CP). In the mutagenesis test, CP exhibited no mutagenecity in the in vitro assay. In the acute toxicity test, CP was administered orally at 0 mg/kg, 1,000 mg/kg, 2,000 mg/kg and 5,000 mg/kg body weight to Wistar rats (five animals/sex/group). No significance changes were observed test article-related during the 14-day observation period. The LD₅₀ of CP was estimated to be more than 5,000 mg/kg body weight in rats. In the subacute toxicity test, CP was administered at 0%, 2.5%, 5% and 10% in pelleted rodent diet to Wistar rats (ten animals/sex/groups). No mortality or treatment-related clinical signs were observed in any of the groups during the 28-day observation period. In both sexes, renal histopathology was conducted in the control and 10% groups, because absolute and relative renal weights increased in the 10% groups compared to the control groups. Based on the histopathology of the kidneys, the no-observed-adverse-effect level (NOAEL) is greater 8.57 g/kg body weight/day for males and 8.62 g/kg body weight/day for females.