Abstract This study determined the supplemental effects of Lactobacillus extract (LBE) postbiotics on intestinal health and prevention of postweaning diarrhea caused by F18+ Escherichia coli (ETEC) in nursery pigs. Sixty-four weaned pigs (6.6 ± 0.7 kg BW) were allotted in a RCBD to 4 dietary treatments (NC: no-challenge; PC: challenge/no-treat; BMD: challenge/bacitracin; LBE: challenge/LBE 0.2%) and fed diets for 28 d. At d 7, challenged groups were orally inoculated with ETEC (2.4 x 1010 CFU) and NC group received sterile solution. Growth performance was analyzed weekly and pigs were euthanized on d 28 to measure intestinal health. Data were analyzed using the SAS 9.4. During post-challenge period, PC tended to decrease (P = 0.067) ADG (373 to 284 g/d), whereas BMD increased (P < 0.05) ADG (284 to 408 g/d); LBE tended to increase (P = 0.081) ADG (284 to 370 g/d). PC increased fecal score (P < 0.05, 3.4 to 3.9) on d 14, whereas BMD decreased it (P < 0.05, 3.9 to 3.5) on d 21. PC increased (P < 0.05) protein carbonyl (0.76 to 1.12 nmol/mg protein), crypt cell proliferation (28 to 36%), and Helicobacter rodentium (0.4 to 3.7%). However, BMD decreased (P < 0.05) crypt cell proliferation (36 to 32%) and Helicobacter spp. (15.0 to 1.4%); and increased (P < 0.05) villus height (309 to 377 µm), Bifidobacterium boum (0.04 to 2.0%), Pelomonas spp. (1.5 to 8.5%), and Microbacterium ginsengisoli (0.5 to 3.0%). LBE reduced (P < 0.05) crypt cell proliferation (36 to 27%) and Helicobacter rodentium (3.7 to 0.04%); and increased (P < 0.05) Lactobacillus salivarius (0.3 to 4.1%) and Propionibacterium acnes (0.4 to 7.4%). Collectively, ETEC reduced growth performance by adversely affecting microbiota and intestinal health. BMD and LBE improved growth performance by enhancing intestinal health and increasing beneficial microbiota in ETEC challenged pigs.