Macrofungi are key decomposers of organic matter and play an active role in biogeochemical cycles, thereby contributing to carbon sequestration in forest ecosystems. Floodplain forests (várzeas) are characterized by the dynamics of rising and receding waters, which are rich in suspended material and influence species variation and adaptation. The knowledge about the distribution of macrofungi in várzea environments in the Brazilian Amazon is limited. This study aims to evaluate the diversity and composition of macrofungi on three várzea forest islands, while also examining differences in species richness and abundance between seasonal periods. A total of 88 macrofungal species that belong to the phylum Basidiomycota were identified. The findings revealed significant variations in species composition, yet no notable differences in species richness or abundance were observed between the seasonal periods. The environmental conditions and resources available to macrofungi appear to be consistent among the islands, which leads to a balanced diversity. However, additional research is essential to uncover the true distribution patterns of macrofungi in the várzeas of the Brazilian Amazon, an area under significant threat to its biodiversity.