Three new species of Marasmius are described herein with their uniqueness supported by full morphological and taxonomic examination. Marasmius cantareirensis and M. fuligineo-ochraceus belong to sect. Marasmius subsect. Sicciformes while M. pulberistipitatus is a representative of sect. Globulares. All specimens were collected in the Atlantic Rainforest in Southeastern Brazil. Detailed micro and macromorphological descriptions are provided for each taxon, followed by illustrations and taxonomic comments.