Aims: To investigate the effect of whey protein concentrate (WPC) enriched in anti-Helicobacter pylori antibodies on growth of the organism in vitro. Methods and Results: A WPC rich in H. pylori-specific antibodies was produced by immunizing lactating cows against H. pylori and processing pooled bulk milk samples into whey powder. The antibodies bound several proteins within the bacterial homogenate and were active at pH 5. In a complement-dependent reaction, the immune WPC was highly bactericidal against four H. pylori strains tested in vitro. Conclusions: WPC produced with milk from H. pylori-immunized cows contains antibodies that are active at the pH of the stomach, and bactericidal against H. pylori in vitro, via the classical complement pathway. Significance and Impact of the Study: This study has demonstrated the potential for use of WPC in the prevention/treatment of H. pylori infections.