The purpose of this study was to evaluate the mutagenicity and safety of water extract of fermented Toona sinensis Roemor leaves (WFTS). The WFTS was prepared by fermenting Toona sinensis Roemor leaves anaerobically for 14 d, and then extracting with boiling water. The mutagenic effects of WFTS were investigated using Ames test. No mutagenicity was found toward all tester strains (Salmonella typhimurium TA98, TA100, TA102, TA1535). In the acute oral toxicity study, a single limit dose of 2.5 or 5 g/kg body weight (bw) WFTS was given to male Sprague-Dawley (SD) rats, then the rats were observed for 14 d. No acute lethal effect at a maximal dose of 5 g/kg bw WFTS was observed in rats. In the subacute study, the male rats were administered daily by gavage at a dose of 0.5 or 1 g/kg bw/d of WFTS for 28 d. The results indicated that no significant toxic effect was found in the parameters of body and organ weight, as well as hematological, biochemical, urinary, and pathological parameters between control and the WFTS-treated rats. The level of no observed adverse effect level (NOAEL) of WFTS in male rats was 1 g/kg bw for subacute toxicity study.