Despite the continued clinical application of traditional herbal medicines, scientific evidence such as toxicological safety profile of Yongdamsagan-tang water extract (YSTW) has not yet been established. The purpose of this study was to investigate the potential toxicity profile of YSTW following a 13-week repeated oral administration at various concentrations to Sprague Dawley rats. YSTW was administered orally to rats once daily at doses of 0, 1000, 2000, and 5000 mg/kg bw/day for 13 weeks. During the experimental period, there were no significant toxicological changes related to YSTW treatment. These results indicate that the administration of YSTW for 13 weeks in the rat resulted in no signs of toxicity at up to 5000 mg/kg bw/day, which was considered the no-observed-adverse-effect level.