Raw milk is a recognized source of Campylobacter outbreaks, but pasteurization is an effective way to eliminate the causative agent of Campylobacteriosis. Whereas breastfeeding is protective against infectious diseases, consumption of formula milk is thought to be not. However, in relation to Campylobacter, such data is currently unavailable. Although both pasteurized and formula milk are pathogen free and prepared in a quality controlled manner, the effect they have on the virulence of Campylobacter species is unknown. Here, we studied the effect of cow, goat, horse, and formula milk on Campylobacter invasion into intestinal epithelial Caco-2 cells, a pathogenic feature of this bacterial species, using a gentamicin exclusion invasion assay. We found that all milk products modulated the invasion of Campylobacter species into the Caco-2 cells in a dose-dependent manner. Control experiments showed that the milks were not toxic for the Caco-2 cells and that the effect on invasion is caused by heat labile (e.g., milk proteins) or heat stable (e.g., sugar/lipids) components depending on the Campylobacter species studied. This in vitro study shows for the first time that pasteurized and formula milk affect the invasion of Campylobacter. We recommend a prospective study to examine whether pasteurized and formula milk affect Campylobacteriosis.