To evaluate the effect of Pseuderanthemum palatiferum, a new medicinal plant, on piglets′ daily weight gain and the effect on piglets with diarrhea, a total of 644 piglets (396 suckling and 248 weaned piglets) were examined using 3 tests for 30 days. Fresh leaves or dried leaf-powder of P. palatiferum were fed daily at different dosages or for different durations to the piglets. The dose of P. palatiferum to both suckling and weaned piglets could improve the following parameters: growth rate became higher; retarded growth, diarrhea and mortality were decreased; and the number and duration of diarrhea cases were decreased. The dosage during 30 days was more effective than that during 7 days and the leaf-powder dosage of 0.2 g/kg body weight (BW)/day was more effective than that of 0.1 g/kgBW/day. The effect of the dried leaf-powder was the same as or equivalent to the fresh-leaf. It also kept the piglets in a healthy physiological condition. It is expected that the usage of this plant, especially in the form of leaf-powder, has a high possibility to replace or reduce the amount of antibiotics in pig production systems in future.