A total of 150 crossbred pigs [(Duroc × Yorkshire) × Landrace; body weight (BW) = 5.74 ± 1.15 kg; weaned at day 21 after birth] were assigned to one of five dietary treatments (six pens per treatment and five pigs per pen) by BW and sex (two barrows and three gilts) for a 6 wk experiment. The pen was considered the experimental unit in the statistical model. Treatments were corn–soybean meal diets supplemented with 0.0033% tiamulin as well as 0%, 0.05%, 0.10%, or 0.20% fermented garlic (FG). The average daily gain, average daily feed intake (ADFI), and feed conversion ratio were linearly (p < 0.05) increased by FG inclusion during days 21–42 and days 0–42. Dietary supplementation of FG linearly increased (p < 0.05) the coefficient of apparent total tract digestibility of dry matter, nitrogen, and gross energy as well as blood immunoglobulin G concentration during week 6. The fecal ammonia (NH₃), total mercaptan emissions, and Escherichia coli counts were linearly (p < 0.05) reduced by FG in the diet. Dietary supplementation of FG increased (p < 0.05) ADFI during days 21–42 and days 0–42 and reduced (p < 0.05) fecal NH₃ emissions compared with pigs fed tiamulin. In conclusion, the results indicate that FG can enhance growth performance and digestibility, and reduce fecal E. coli counts as well as fecal gas emissions in weanling pigs.