This study was performed in order to determine whether human isolated probiotic bacteria can be effective in reducing Campylobacter jejuni infection of chicken intestinal cells, in vitro, and in decreasing its colonization abilities within the chicken gut. Our results show that the probiotic strains Lactobacillus paracasei J. R, L. rhamnosus 15b, L. lactis Y, and L. lactis FOa had a significant effect on C. jejuni invasion of chicken primary cells, with the strongest inhibitory effect detected when a combination of four was administered. In regard to the in vivo effect, using all four strains in one combination prevented mucus colonization in the duodenum and cecum. Moreover, the pathogen load in the lumen of these two compartments was significantly reduced. When probiotics were introduced during the early growth period, the presence of the pathogen in feces was increased (p>0.05), but when they were given during the last week of growth, there was no significant effect. In conclusion, our data indicate that these four new probiotic strains are able to cause modifications in the chicken intestinal mucosa and can reduce the ability of C. jejuni to invade, in vitro, and to colonize, in vivo. These probiotics are now proven to be effective even when introduced in broiler's feed 7 days before slaughter, which makes them cost-effective for the producers.