Among ferns, the leatherleaf fern (Rumohra adiantiformis) is of particular economic importance. The fronds are sold around the world for flower arrangements. In Brazil, these fern fronds represent an income source for numerous households, working with a traditional management system with a maximum of three annual collections in the same area. The purpose of this study was to evaluate the demographic structure of managed R. adiantiformis populations in the south of Brazil and verify the sustainability of the harvesting activity in this region. The study was conducted in an area of Atlantic Rainforest in the State of Rio Grande do Sul. The demographic structure of the managed populations was evaluated in permanent plots, where fronds in the different development phases were counted quarterly for one year. Rainfall was identified as the main factor influencing bud emergence and development. A reduction in R. adiantiformis populations related to forest regeneration was also observed. Fast frond regeneration and the absence of differences between managed and non-managed populations concerning the proportions of buds and young fronds corroborate the ecological sustainability of the management system used by the local harvesters. The results obtained differ largely from those of populations studied in South Africa, where R. adiantiformis plants seem unable to maintain frond density and size when harvested. These contrasting results are probably related to climatic differences between these areas, especially annual rainfall, which is higher in Brazil allowing for the rapid regeneration and sustainable management of this resource in the Brazilian Atlantic Rainforest.