A study was conducted to evaluate the effects of 3 different plant extracts on diarrhea, immune response, intestinal morphology, and growth performance of weaned pigs experimentally infected with a pathogenic F-18 Escherichia coli (E. coli). Sixty-four weaned pigs (6.3±0.2 kg BW, and 21 d old) were housed in individual pens in disease containment chambers for 15 d: 4 d before and 11 d after the first inoculation (d 0). Treatments were in a 2×4 factorial arrangement: with or without an F-18 E. coli challenge (toxins: heat-labile toxin, heat-stable toxin b, and Shiga-like toxin 2; 10(10) cfu/3 mL oral dose; daily for 3 d from d 0) and 4 diets [a nursery basal diet (CON) or 10 ppm of capsicum oleoresin, garlic botanical, or turmeric oleoresin]. The growth performance was measured on d 0 to 5, 5 to 11, and 0 to 11. Diarrhea score (1, normal, to 5, watery diarrhea) was recorded for each pig daily. Frequency of diarrhea was the percentage of pig days with a diarrhea score of 3 or greater. Blood was collected on d 0, 5, and 11 to measure total and differential white blood cell counts and serum tumor necrosis factor (TNF)-α, IL-10, transforming growth factor (TGF)-β, C-reactive protein, and haptoglobin. On d 5 and 11, half of the pigs were euthanized to measure villi height and crypt depth of the small intestine and macrophage and neutrophil number in the ileum. The E. coli infection increased (P<0.05) diarrhea score, frequency of diarrhea, white blood cell counts, serum TNF-α and haptoglobin, and ileal macrophages and neutrophils but reduced (P<0.05) villi height and the ratio of villi height to crypt depth of the small intestine on d 5. In the challenged group, feeding plant extracts reduced (P<0.05) average diarrhea score from d 0 to 2 and d 6 to 11 and frequency of diarrhea and decreased (P<0.05) TNF-α and haptoglobin on d 5, white blood cell counts and neutrophils on d 11, and ileal macrophages and neutrophils on d 5. Feeding plant extracts increased (P<0.05) ileal villi height on d 5 but did not affect growth performance compared with the CON. In the sham group, feeding plant extract also reduced (P<0.05) diarrhea score, frequency of diarrhea, and ileal macrophages compared with the CON. In conclusion, the 3 plant extracts tested reduced diarrhea and inflammation caused by E. coli infection, which may be beneficial to pig health.