The yeastSaccharomyces boulardiiCNCM I-745 is a unique, non-bacterial microorganism classified as a probiotic agent. In this review article, at first, we briefly summarized the mechanisms responsible for its probiotic properties, e.g. adhesion to and elimination of enteropathogenic microorganisms and their toxins; extracellular cleavage of pathogens' virulent factors; trophic and anti-inflammatory effects on the intestinal mucosa. The efficacy ofS. boulardiiadministration was tested in variety of human diseases. We discussed the results ofS. boulardiiCNCM I-745 use in the treatment or prevention ofHelicobacter pyloriinfections, diarrhoea (Clostridium difficileinfections, antibiotic-associated diarrhoea, and traveller's diarrhoea), inflammatory bowel diseases, irritable bowel syndrome, candidiasis, dyslipidemia, and small intestine bacterial overgrowth in patients with multiple sclerosis. In case of limited number of studies regarding this strain, we also presented studies demonstrating properties and efficacy of other strains ofS. boulardii.Administration ofS. boulardiiCNCMI I-745 during antibiotic therapy has certain advantage over bacterial probiotics, because-due to its fungal natural properties-it is intrinsically resistant to the antibiotics and cannot promote the spread of antimicrobial resistance. Even though cases of fungemia followingS. boulardiiCNCM I-745 administration were reported, it should be treated as a widely available and safe probiotic strain.