Describing spatial variation in species richness and understanding its links to ecological mechanisms are complementary approaches for explaining geographical patterns of richness. The study of elevational gradients holds enormous potential for understanding the factors underlying global diversity. This paper investigates the pattern of species richness and range-size distribution of epiphytic bryophytes along an elevational gradient in Marojejy National Park, North-east Madagascar. The main objectives are to describe bryophyte species composition and endemism in Marojejy National Park, to describe the species richness and distribution patterns of epiphytic bryophytes along an elevational gradient from 250 m to 2050 m and to evaluate the explanatory value of environmental variables for the observed patterns. Bryophyte samples were collected following a nested design with four hierarchical levels: elevational belts, plots, quadrats and microplots. In total, 254 epiphytic bryophyte species were recorded, comprising 157 liverworts and 97 mosses. Twenty-three of these are endemic to Madagascar. Species richness exhibits a hump-shaped pattern along the elevational gradient, peaking at 1250 m. Eighty seven percent of the total recorded species have a range distribution lower than 1000 m, at which point 36% are restricted to these single elevations. Our results suggest that mean temperature, relative humidity and vapour pressure deficit play important roles in shaping the richness pattern observed in this study. While the liverwort richness pattern did not correlate to vapour pressure deficit and responded only weakly to relative humidity, the richness pattern shown by mosses correlates well with mean temperature, relative humidity and vapour pressure deficit.