This experiment was conducted to evaluate various levels of milk by-products in weaned pig's diet on growth performance, blood profiles, diarrhea incidence, and intestinal morphology of weaned pigs. A total of 160 weaned pigs ([Yorkshire × Landrace] × Duroc), average 5.97 ± 1.53 kg body weight (BW), were allotted to 1 of 4 treatments in 5 replications with 8 pigs per pen by BW. Pigs were fed each treatment diet with various levels of milk by-products (phase 1: 5%, 10%, 20% or 30%; phase 2: 0%, 5%, 10% or 15%) for 5 weeks. Linear increase of BW, average daily gain, average daily feed intake, and gain to feed ratio with increasing milk by-products was observed in whole experimental period (linear response, p < 0.05). In blood profiles, however, there were no differences in blood urea nitrogen, insulin like growth factor 1, and immunoglobulin A and G among the treatments. In addition, no differences were found in diarrhea incidence and intestinal morphology. In conclusion Increasing milk by-product content in the diets of weaned pigs improved growth performance but high or low level of milk by-product content did not negatively affect blood profiles, diarrhea incidence, and gut health of nursery pigs.