Indonesia’s low-quality cacao beans are due to the lack of fermentation, a crucial process for developing flavor precursors driven by yeast, lactic acid bacteria (LAB), and acetic acid bacteria (AAB) activities. Natural spontaneous fermentation requires large bean quantities in which the nature of the microbiome tends to be inconsistent and in low concentrations. From the commonly found microbes in spontaneous cacao fermentation, Saccharomyces cerevisiae, Lactobacillus lactis, Lactobacillus plantarum, and Acetobacter aceti have been the most studied starter cultures. Furthermore, these starter cultures can be added in dried form to make it easier to apply in the fermentation. This research aimed to determine the effect of different rice flour concentrations (30%, 40%, 50%, and 60%) as carrier material towards the yield, viability, and moisture content of dry starter cultures, and the effect of different microbial ratios in dry starter cultures (1:1:1, 2:1:1, 1:2:1, 1:1:2 of Saccharomyces cerevisiae, Lactobacillus fermentum, and Acetobacter pasteurianus) on cacao bean fermentation. Results showed that rice flour concentration significantly influenced yield, with the best concentrations being 50% for S. cerevisiae and L. fermentum and 60% for A. pasteurianus. The dry starter cultures had a viability of 8–9 log CFU/g with high moisture content (25– 36%). The dried starter cultures were further applied in cacao bean fermentation in different ratios. The 1:1:1 ratio, using 50% rice flour concentration for S. cerevisiae and L. fermentum, and 60% rice flour for A. pasteurianus resulted in higher values of temperature, pulp pH, bean TTA, and fermentation index (FI). Cacao beans in this research were not fully fermented due to shallow fermentation depth and inadequate cacao mass.