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The beneficial effects of probiotic Enterococcus spp. in different hosts, such as mice and humans, have previously been reported in several studies. However, studies of large domestic animals, as well as challenge studies with pathogenic microorganisms, are very rare. Here, we investigated the influence of oral treatment of pigs with the probiotic bacterium Enterococcus faecium NCIMB 10415 on Salmonella enterica serovar Typhimurium DT104 infections in weaning piglets. Clinical symptoms, fecal excretion, the organ distribution of Salmonella, and the humoral immune response (immunoglobulin G [IgG], IgM, and IgA levels) in serum were examined. A pool of 89 piglets was randomly divided into probiotic and control groups. The probiotic group received a feed supplement containing E. faecium starting on day 14 postpartum prior to challenge with Salmonella serovar Typhimurium DT104 at 28 days postpartum. After challenge with Salmonella serovar Typhimurium DT104, piglets in both groups showed no severe clinical signs of salmonellosis. However, fecal excretion and colonization of Salmonella in organs were significantly greater in piglets fed E. faecium. Likewise, the humoral immune response against Salmonella (serum IgM and IgA levels) was significantly greater in the probiotic group animals than in control animals. The results of this study suggest that E. faecium NCIMB 10415 treatment enhanced the course of infection in weaning piglets challenged with Salmonella serovar Typhimurium DT104. However, the probiotic treatment also appeared to result in greater production of specific antibodies against Salmonella serovar Typhimurium DT104.