Probiotics are living microorganisms (e.g., bacteria) that are either the same as or similar to organisms found naturally in the human body and may be beneficial to health. Current researches have shown that the balance between beneficial and pathogenic bacteria is essential in order to maintain the oral health. Therefore, oral cavity has recently been suggested as a relevant target for probiotic applications. Dental caries can be seen as a microbial imbalance where the oral microbiota shift towards community dominance which produces acidogenic and acid-tolerant gram positive bacteria. Similarly, the accumulation of bacteria within the biofilm, facilitated by poor oral hygiene, predisposes to allogenic shifts in the microbial community, leading to the onset of periodontal inflammation. Probiotic bacteria belonging to the genus of Lactobacillus, Bifidobacterium and Streptococcus have been proven effective for preventing caries by reducing the number of cariogenic bacteria in saliva after a short period of consuming the probiotic. In contrast, the effect of probiotics on improving gingivitis and periodontitis has been less investigated. The currently available studies on the effect of probiotics on periodontal pathogens and clinical periodontal parameters showed differing results depending on the strains used and the endpoints analyzed. Many of the clinical studies are pilot in nature and with low quality, therefore, properly conducted clinical trials, using probiotic strains with in vitro proven periodontal probiotic effects, are needed. The putative beneficial effects of probiotics on oral malodour have also been evaluated, but further evidence is needed to fully explore the potential of probiotics for preventing malodour.