Proteins in bovine milk are a common source of bioactive peptides. The peptides are released by the digestion of caseins and whey proteins. Peptides derived from the different genetic variants A, B, C, E, F1, F2, G1, G2, H, I, and J of bovine kappa-casein (CSN3) were investigated for their inhibitory activities against angiotensin I converting enzyme (ACE). Amino acid sequences of the CSN3 variants were analyzed in silico to detect potential ACE inhibitory peptides. Besides known biologically active peptides, exclusive peptides were identified in some CSN3 variants and their biological activity was determined: within CSN3*B and CSN3*C, the ACE inhibitory peptide ASP (IC50 = 242.3; the IC50 value is equivalent to the micromolar concentration of peptide mediating a 50% inhibition of ACE activity) and within CSN3*C the peptide AHHP (IC50 = 847.6) was detected. Furthermore, the peptides VSP (IC50 = 21.8) and ACHP (IC50 = 360.7) were identified in CSN3*F1 and CSN3*G2, respectively.