The richness and ecological roles of yeasts in peatlands are largely unknown. This paper presents a review of the literature on yeasts in peatlands and also provides new data with species isolated from peatlands in Saskatchewan, Canada, and West Siberia, Russia. To date, 75 yeast taxa have been reported from peatlands, including 46 identified species and 29 isolates identified only to genus or not at all. This represents 5%–10% of known yeasts and about 10% of all peatland fungi. Cryptococcus, Candida, Pichia, and Rhodotorula are the most prevalent genera, accounting for 58% of known peatland yeast species. We obtained 34 isolates from western Canadian and West Siberian bog and fen peat, including 12 identified species and eight unidentified taxa. Identified taxa comprised mostly species of Candida, Cryptococcus, and Rhodotorula. Unidentified taxa were described based on physiology and morphology. Globally, more species have been reported from bogs than fens (41 vs. 13 taxa), and the species composition differs between the two peatland classes. The effect of depth within the acrotelm on yeast abundance and species composition varies among peatlands. Physiological profiling of the yeasts from our study showed that they can use (poly)saccharides (primarily D-glucose, maltotriose, n-acetyl glucosamine, trehalose, and sucrose), organic acids (primarily D-gluconic acid, fumaric acid, malic acid, and succinic acid), sugar alcohols (primarily D-arabitol, D-mannitol, and D-sorbitol), glycosides (primarily arbutin and salicin), and amino acids (primarily L-glutamic acid) as carbon and nitrogen sources. Based on these profiles, yeasts likely access simple polymers that leach from senesced and/or dead plant materials in peatlands and probably play important roles during the initial stages of organic matter decomposition.