Bacteriocins are antimicrobial peptides produced by a wide range of bacteria. Their antineoplastic properties have been inadequately revealed in the late 70s by using crude bacteriocin preparation toxic to mammalian cells. Nowadays, purified bacteriocins are available and have shown inhibitory properties toward diverse neoplastic line cells. Pyocin, colicin, pediocin, and microcin are among bacteriocins reported to present such activity. Moreover, modified bacteriocins proved to be effective in a glioblastoma xenograft mouse model. Screening for the presence of bacteriocin in colon cancer subjects has been studied with mixed results. Bacteriocin use as a therapeutic agent or in a prevention setting is discussed specifically evaluating bacteriocins biochemical properties and recent advances in peptide therapeutics.