Prototheca are unicellular, achlorophyllous, yeast-like microalgae that have been implicated as the causative agents of opportunistic infections in animals and humans, collectively referred to as protothecosis. Still, the algae are typically saprophytic in nature and mostly occur in areas of high humidity and high organic matter content. Only a few recent studies have explored the environmental reservoir of Prototheca. This work is the first study since the early 1980s to investigate the prevalence of Prototheca spp. in natural terrestrial sources. A total of 226 soil samples were collected, with only 10 yielding Prototheca growth. The overall isolation rate of the algae was 4.4%, with the predominant species being Prototheca bovis. These results show that Prototheca algae only sporadically occur in soils of the temperate climatic zone. Consequently, this work contradicts the ubiquity of Prototheca in soils, breaking the paradigm that, despite the lack of serious experimental appraisal, has long been perpetuated in the literature.