The influence of Ca-Montmorillonite (Ca-MNT) and zeolite NaY addition on ethanol production from synthetic molasses by S. cerevisiae 251 TP(3-2) was studied by the measurement of biomass concentrations and metal ion concentration with respect to fermentation time. Addition of 5 g/L Ca-MNT and 10 g/L zeolite NaY resulted in an increase in both ethanol concentration and ethanol production rate. This increase was 24 and 40% for ethanol concentration and 65 and 87% for production rate, respectively. From the ion analyses, it was observed that the NaY added to the medium decreased the toxic concentration of zinc, manganese, and iron cations and acted also as a pH regulator. Ca-MNT added to the medium decreased the concentration of Na+ ions, which is known to have a toxic effect on glycolysis and cell concentration. These effects caused improvement in the ethanol production rate.