PM014 is a modified herbal formula based on Chung-Sang-Bo-Ha-Tang, which is a well-known prescription drug used for curing various inflammatory pulmonary diseases. We previously showed that PM014 attenuated lung inflammation in a murine model of chronic obstructive pulmonary disease (COPD). The objective of the present study was to evaluate the chronic oral toxicity of PM014 in rats. PM014 was administered to rats orally once daily at doses of 0, 750, 1500, and 3000 mg/kg/day for 13 weeks. The PM014 treatment did not result in any toxicologically significant changes between the control and treatment groups in body weight, clinical signs, food consumption, dermatological and serum biochemical parameters, organ weight ratio, or histopathology. We concluded that no PM014-related toxicity was detected even at the highest doses investigated in this repeated dose oral toxicity study. Based on our results, the no-observed-adverse-effect level (NOAEL) of PM014 was 3000 mg/kg/day in both genders. These results might provide supportive evidence of the safety of PM014 to develop a new drug.