The present study investigated the effects of microbial additives producing antimicrobial and digestive-enzyme activities on the growth performance, blood metabolites, and fecal microflora of weaning pigs from 21 to 42 d of age. A total of 144 weaning pigs (1:1 ratio of gilt and boar; 21 d of age; 7.40 ± 0.53 kg of average body weight) were randomly distributed into four supplementary levels of microbial additive (0 vs. 0.5 vs. 1.0 vs. 1.5% of fresh weight) with three pens of replication, consisting of 12 weaning pigs per pen. All weaning pigs were maintained with the same basal diet for 21 d. Blood and feces were subsampled at day 21. Feed efficiency tended to increase linearly (p = 0.069) with an increasing supplementation level. Insulin, insulin-like growth factor 1, and blood glucose presented a quadratic effect (p < 0.05) with an increasing supplementation level, and these blood metabolites were highest at the 1% supplementation level. Immunoglobulin G in blood increased linearly by (p < 0.05) increasing the supplementation level. Salmonella and Escherichia coli in feces were decreased linearly by (p < 0.05) increasing the supplementation level. In conclusion, supplementation of microbial additive at 1.0% improved the feed efficiency, blood metabolites, and fecal microflora of weaning pigs.