Porcine edema disease (ED) is caused by Shiga toxin 2e-producing Escherichia coli (STEC). ED has become frequent in pig farms, and the use of antimicrobials has resulted in the development of antimicrobial-resistant STEC. Accordingly, the use of materials other than antimicrobials is requested for the prevention of ED. Oral administration of a heat-killed and dried cell preparation of Enterococcus faecalis strain EC-12 (EC-12) to weaning pigs was previously demonstrated to decrease animal mortality in a STEC-contaminated farm at 0.05% (w/w) dose level. In this study, pigs experimentally infected with STEC were used as a model for ED to evaluate the low dose level of EC-12 to prevent ED. Fifteen 21-day-old pigs were divided into 5 groups: STEC challenge with the basal diet, STEC challenge with EC-12 supplemented at 0.005, 0.01, or 0.05% (w/w) to the basal diet, and no STEC challenge with the basal diet. The challenge was carried out when the animals were 25, 26, and 27 days old using STEC contained in capsules resistant against gastric digestion. All pigs were euthanized at 32 days of age. The daily weight gain, feed conversion ratio, and palpebral edema were improved by supplementation with 0.05% EC-12, but not by the low dose levels. Accordingly, 0.05% level of supplementation was needed for EC-12 to improve clinical symptoms in weaning piglets infected by STEC.