Tempe, a fermented soybean product, plays a significant role in Indonesian dietary culture. Currently, there have been no studies that classify tempe as a functional food using up-to-date genomic data. This research used an Illumina-based meta-transcriptomic method to explore the microbial communities that mainly contribute to tempe fermentation and their functions related to its health benefits. The analysis revealed 8 phyla, 19 families, 20 genera, and 28 species of both bacteria and fungi. The dominant species found were Klebsiella africana, followed by Rhizopus microsporus, Klebsiella pneumoniae, Rhizopus oligosporus, Propionibacterium humerusii, and Lactobacillus brevis. Klebsiella and Propionibacterium are involved in vitamin B12 production, while Rhizopus is associated with GABA production and isoflavones like genistein and daidzein, along with spermidine, caffeic acid, and chlorogenic acid. Lactobacillus contributes proteases, GABA, and beta-glucosidase. The study also strengthened the link between microbes and health benefits by identifying certain microbial genes and their expression levels in the samples. Changes in gene expression reveal how fermentation environments affect diversity and functionality. Overall, finding a variety of bioactive compounds and their genetic backgrounds supports tempe's position as a functional superfood that could gain global popularity through further research and development.