This study aimed to prepare peptides from buffalo milk's casein and to examine the antimicrobial effect of these casein peptides against diverse foodborne microorganisms. Casein was prepared by acid precipitation of buffalo's skimmed milk, and was found to consist of protein (83.19%), moisture (11.45%), ash (2.6%), fat (1.6%), and lactose (0.53%). Peptides were prepared from dried acid casein by  proteolysis with chymosin and were dissolved to produce peptide concentrations of 10%, 20% 30%, and 40% (w/v%). These casein peptide preparations were assessed for their antimicrobial activity against Gram-positive, Gram-negative bacteria and yeasts. The antimicrobial effect of casein peptide solutions depended on the examined microorganism and the peptide concentration. Salmonella ser. Typhimurium, Cronobacter sakazakii, Kluyveromyces marxianus, and Kodamaea ohmeri could be variably inhibited by all casein peptide concentrations ranging from 10% to 40%. Whereas, Escherichia coli stains, and Klebsiella pneumonia could only  be inhibited by solutions containing more than 10% casein peptides.  Shigella flexneri, Issatchenkia orientalis, Candida catenulate, and Clavispora lusitaniae could only be inhibited by casein peptides concentrations higher than 20%.  Candida albicans showed the highest resistance to casein peptides, as it could only be inhibited with the use of 40% casein peptides. These results showed that peptides prepared from acid casein by proteolysis with chymosin had an inhibitory effect against divers Gram-positive and Gram-negative bacteria and yeasts.