Background <p>Ethnomycological studies explore the relationships between humans and fungi, often reflecting cultural practices and ecological knowledge. While such studies have expanded across Brazil, the Southern region remains understudied. This research aims to document the ethnomycological knowledge of Polish and Ukrainian immigrant descendant communities in a subtropical area in Southern Brazil, and discuss the persistence, transformation, and erosion of mycological knowledge.</p> Methods <p>Fieldwork was conducted in rural areas of Itaiópolis and Papanduva (Santa Catarina, Brazil), with 35 participants interviewed using semi-structured methods. A photographic catalog was used to support species identification. Fungal specimens were collected, morphologically identified, and in some cases, DNA barcoded. The data were analyzed qualitatively.</p> Results <p>A total of 19 fungal species were reported, with <i>Agaricus</i>, <i>Armillaria</i>, <i>Macrolepiota</i>, and <i>Auricularia</i> being the most cited genera. Mushrooms were primarily used as food, though medicinal, ornamental, recreational, and symbolic uses were also documented. Traditional recipes and vernacular names in Polish and Ukrainian were preserved, illustrating cultural continuity. Some reports suggest stock knowledge persists, even when active use has declined.</p> Conclusions <p>The study reveals that mushrooms remain culturally significant among immigrant descendant communities in Southern Brazil. While some traditional knowledge is preserved and even adapted, other aspects show signs of erosion or restricted transmission. The findings highlight how immigration, environmental factors, and cultural resilience interact in shaping mycological knowledge. This research contributes to the broader understanding of how human-fungus relationships evolve in migratory contexts and calls attention to the importance of preserving biocultural heritage.</p>