Abstract Foodborne diseases are caused by consuming food contaminated with pathogens such as bacteria, viruses, parasites, or toxic chemicals, as well as biotoxins. Bacteria responsible for foodborne disease include Escherichia coli and Staphylococcus aureus. The typical approach to managing foodborne disease involves the use of antibiotics, which might lead to resistance over time. Kefir is a probiotic drink that can help maintain health by balancing the natural gut microflora. This study aims to investigate the impact of adding butterfly pea powder to kefir on its antibacterial activity against the bacteria that cause foodborne disease. Kefir was prepared by adding butterfly pea powder in six different concentrations (0%, 0.5%, 1%, 1.5%, 2%, and 2.5%) with four replications. Kefir’s pH, total titrated acid, total LAB, and its antibacterial activity using the microdilution method were observed. The results revealed that the addition of butterfly pea flower powder at various concentrations significantly influenced the pH value, total acidity, and antibacterial effects against E.coli and S.aureus but did not significantly affect the total LAB count. Butterfly pea flower powder reduced the pH value, increased the total acidity, and enhanced the antibacterial activity, resulting in a higher percentage of inhibition against the tested bacteria without adversely affecting LAB growth. It was concluded that adding butterfly pea powder to cow milk kefir potentially improves the antibacterial functions against bacteria causing foodborne disease.