β-lactoglobulin (BLG) and ε-polylysine (PL) were bound by using microbial transglutaminase. Dextran (Dex) was further conjugated to the BLG-PL conjugate by the Maillard reaction. Confirmation of conjugation was carried out by SDS-PAGE. From the results of isoelectric focusing, it was revealed that the isoelectric point of the BLG-PL conjugate was shifted to the basic side as compared with native BLG. Immunogenicity of BLG in BALB/c mice was lowered by conjugation with PL and further lowered by conjugation with Dex. By conjugation with PL and PL-Dex, antibacterial activity against Staphylococcus aureus was endowed to BLG. Because the conjugation method in this study is a safe method, it is valuable in that it can be applicable to food processing.