K5 is a lactic acid bacteria (LAB) strain, isolated recently from feta-type cheese. Its probiotic potential has been demonstrated in a series of established tests. Moreover, incorporation of K5 as starter culture offered organoleptic and technological advantages to novel fermented food products. In the present study, further investigation of the potential probiotic activity of K5 was performed and its mechanisms of action were investigated. Employing quantitative analysis and confocal, fluorescent microscopy the adhesion properties of the above strain were studied. K5 displayed efficient adherence capacity to Caco-2 colon cancer cells, similarly to the reference strains ATCC 393 and GG. Moreover, treatment of Caco-2 cells with K5 inhibited cell proliferation in a time-and dose-dependent manner. The anti-proliferative effects appear to be mediated through induction of apoptosis via modulation of expression of specific Bcl-2 family proteins. These results elucidate the mechanisms of action of K5 and enhance its potential probiotic activity.