Psilodercidae (Araneae) make up a remarkably diverse lineage that is endemic to Southeast (SE) Asia and neighboring regions. Studying the diversity dynamics of this group has the potential to shed light on the spatial and historical patterns of diversity and diversification in megadiverse SE Asia. However, a comprehensive species-level phylogeny of psilodercid spiders remains unclear. Based on a decade of fieldwork and taxonomic research, we incorporated fossil information into the most complete species-level phylogeny for 202 extant species to reconstruct evolutionary history and to test how tropical species diversity formation and maintenance are correlated with diversification rates, dispersal events, and time for species accumulation. Our molecular dating analyses and the fossil records indicate that the psilodercid timetree can be explained by ordinal diversification since the Cretaceous. Our reconstructed biogeographic history of the family suggests that in situ speciation is the predominant form of diversification. Furthermore, geographical changes caused by a series of tectonic collision events have affected the distribution pattern of many lineages. Our diversification analyses show no diversification rate changes through time, among lineages, and across geographic space. Thus, time rather than diversification rates or dispersal is the primary cause of species diversity hotspots of psilodercids in SE Asia.