SummaryMountains are often more species‐rich than lowlands. This could be the result of migration from lowlands to mountains, of a greater survival rate in mountains, or of a higher diversification rate in mountains. We investigated this question in the globally distributed family Ericaceae, which includesc. 4426 species ranging from sea level to > 5000 m. We predict that the interaction of low specific leaf area (SLA) and montane habitats is correlated with increased diversification rates.A molecular phylogeny of Ericaceae based onrbcL andmatK sequence data was built and dated with 18 fossil calibrations and divergence time estimates. We identified radiations usingbammand correlates of diversification rate changes using binary‐state speciation and extinction (BiSSE) and multiple‐state speciation and extinction (MuSSE) analyses.Analyses revealed six largely montane radiations. Lineages in mountains diversified faster than nonmountain lineages (higher speciation rate, but no difference in extinction rate), and lineages with lowSLAdiversified faster than high‐SLAlineages. Further, habitat and trait had a positive interactive effect on diversification.Our results suggest that the species richness in mountains is the result of increased speciation rather than reduced extinction or increased immigration. Increased speciation in Ericaceae was facilitated by lowSLA.