Single oral dose and 13-week oral subchronic toxicity studies of fucoxanthin-containing oil extracted from microalga, Chaetoseros sp., were conducted in rats. In the single oral dose study, no mortality and no change related to the test material were observed. Thus, the 50% lethal dose of microalgal fucoxanthin oil is more than 2,000 mg/kg body weight. In the 13-week oral dose study, 0, 20 or 200 mg/kg body weight of microalgal fucoxanthin oil was administered. The fucoxanthin-administered groups, showed no mortality and no abnormalities. This result suggested that the no-observed-adverse-effect level of fucoxanthin-containing oil extracted from microalga Chaetoseros sp. was 200 mg/kg body weight under the tested subchronic dose condition.