Objectives: The purpose of the present study was to investigate the antidiarrheal effects of Anjang-san in mice and rats. Methods: We measured the content of condensed tannin in Anjang-san extract, and observed the effects of Anjang-san on the small intestinal and colonic transport of mice, as well as on mice models of diarrhea induced by castor oil and $MgSO_4$, and on rat models of castor oil-induced enteropooling. Results: Anjang-san showed significant inhibitory effects on abnormally increased small intestinal transit induced by pyridostigmine and neostigmine, and inhibitory effects on large intestinal transit. Anjang-san also exhibited antidiarrheal effects on diarrhea induced by $MgSO_4$, and inhibitory effects on castor oil-induced enteropooling. Anjang-san also improved castor oil-induced diarrhea based on simple numbers without statistical significance. Conclusion: These results demonstrate that Anjang-san has significant antidiarrheal properties and attests to its possible utility in functional diarrheas, irritable bowel syndrome and other gastrointestinal disorders based upon further studies.