Abstract The swine industry has to find ways to make diets more efficient in terms of growth performance and swine intestinal health. Thus, this study was carried out to verify the effect of dietary supplementation of the probiotic, Lactobacillus rhamnosus, on growth performance, frequency of diarrhea, nutrient digestibility, and blood biochemical parameters of weaned pigs. A total of 40 weaned pigs [6.21 ± 0.55 kg of initial body weight (BW)] were assigned to 2 dietary treatments (4 pigs/pen; 5 replicates/treatment) in a randomized complete block design (block: initial BW). This experiment was performed for 4 weeks. Dietary treatments were a commercial basal nursery diet (CON) and CON supplemented with 0.02% Lactobacillus rhamnosus IDCC 3201 (PRO; ILDONG Bioscience Co., Ltd., Pyeongtaek, Republic of Korea). Average daily gain (ADG), average daily feed intake, and gain to feed ratio (G:F) were measured on day 1, 7, 14, and 28. The frequency of diarrhea was measured for the first 2 weeks after weaning. Diarrhea score of each pen was visually estimated from 1 to 5 (1 = normal feces, 2 = moist feces, 3 = mild diarrhea, 4 = severe diarrhea, and 5 = watery diarrhea). For the last week of experimental period, pigs were fed respective dietary treatments containing 0.2% chromium oxide. Fecal samples from randomly selected one pig per pen were collected daily by rectal palpation for the last 3 days. The samples from the diet and feces of each treatment were used to measure the apparent total tract digestibility of dry matter (DM), energy (EN), and crude protein (CP). Serum samples were collected for blood biochemical parameters. Growth performance, nutrient digestibility, and blood biochemical parameters were analyzed by the General Linear Model of SAS. The frequency of diarrhea was analyzed by the Chi-square test. The experimental unit was a pen. Statistical model for growth performance, nutrient digestibility, and biochemical parameters included dietary treatment as a main effect and initial BW as a covariate. Pigs fed PRO had greater (P < 0.05) ADG and G:F than those fed CON from day 1 to 7, and The PRO had greater (P < 0.05) ADG than CON from day 15 to 28. The PRO increased ADG during overall the experimental period (P < 0.10), nutrient digestibility of DM, EN, and CP (P < 0.05) compared with CON. However, no differences were found on frequency of diarrhea and blood biochemical parameters between dietary treatments. In conclusion, the dietary supplementation of Lactobacillus rhamnosus improved growth performance and nutrient digestibility.