This research article published by International Journal of Biosciences, Vol. 18, No. 2, 2021During spontaneous fermentation of cereals; yeasts ferment carbohydrates to produce alcohol and they also provide vitamins, amino acids, peptides, and nucleotides needed by lactic acid bacteria as well as produce flavour compounds. Nevertheless, spontaneous fermentation is prone to yeast contamination from the surroundings which pose a health risk of opportunistic yeast infection. A study was carried out involving culturing, isolation and identification of yeast contaminants present in the local cereal-based beverages namely Kindi, Kimpumu, Togwa and Mbege purposively sampled and collected from Morogoro, Mbeya and Kilimanjaro regions in Tanzania between February and May 2019. The results disclosed 24% of the yeasts actively involved in the fermentation were opportunistic and identified as Candida zeylanoides, Candida albicans, Cryptococcus gattii, Rhodotorula minuta, Candida ciferrii, and Candida dubliniensis. Such contamination levels from the studied samples sets a base for further research to establish mechanisms of reducing exposure of cereal-based beverage consumers to pathogenic effects of the opportunistic yeasts which may include infections by Candida spp.