Traditional attempts to delineate floristic regions typically focus on species distributions, often ignoring the rich context that phylogenetic relationships can provide. In this study, we explore how phylogenetic relatedness, taxonomic composition, and regional phylogenetic structure change across a global biodiversity hotspot region, Yunnan, located in southwestern China. We propose a system of floristic regions within Yunnan by combining data on the distributions and phylogenetic relationships of 1,983 genera of native seed plants. We identified eight distinct floristic regions in Yunnan, which were grouped into two larger northern and southern geographical units. Phylogenetic relatedness was well correlated with taxonomic composition between floras in Yunnan. Across the Yunnan region we examined, the central Yunnan region shows the lowest level of spatial turnover in phylogenetic relationships and taxonomic composition of the floristic assemblages. Using null model analyses, we found evidence of nonrandom phylogenetic structure across the region, in which four areas show higher phylogenetic turnover than expected given the underlying taxonomic composition between sites. Our results show that the integration of phylogenetic information can provide valuable insight in floristic assessments, and help us to better understand the structure of a global biodiversity hotspot.