This study aimed to investigate the effect of Saccharomyces cerevisiae on the formation of gamma-aminobutyric acid (GABA) and the other bioactive amines during wort fermentation. Within 8 days of fermentation, GABA concentration increased to 182.80 and 534.10 mg/L in unspoiled and spoiled worts, respectively. Although formation of tyramine and histamine did not occur in unspoiled wort, 142 mg/L of tyramine and 130 mg/L of histamine were found in spoiled wort at the end of fermentation. Decreased concentrations of tyrosine and histidine were associated with increased concentrations of tyramine and histamine, respectively, in spoiled wort. The results indicated that S. cerevisiae is a causative agent for the accumulation of GABA in wort during fermentation. Therefore, occurrence of GABA in beers should not be considered as one of the indicators of microbial contamination differently from tyramine and histamine.