The island of Borneo is the diversity center of the Dipterocarpaceae, the most important family of tropical rainforest trees in Southeast Asia. However, changes in land use and climate have affected dipterocarp distributions on the island, raising concerns about the vulnerability (inter alia) of the endemic riparian species Shorea macrophylla. Thus, to aid conservation efforts we have investigated the genetic diversity, structure and demographic history of S. macrophylla. The species’ genetic diversity and structure in Kalimantan (part of Indonesia, covering 75% of the island) was explored by examining genotypes of 377 individuals representing 13 populations in three regions (Northeast, Central and West Kalimantan) using 14 newly developed microsatellite loci. Higher genetic diversity was found, at all loci, in samples from Northeast Kalimantan than in samples from the other regions. Moderate genetic differentiation between populations was detected (FST: 0.093). Bayesian clustering, principal coordinate, and neighbor joining tree analysis of the population structure consistently identified two genetically distinct groups, one in the Northeast and the other in the Central and West regions. The higher diversity of the diverged populations in Northeast Kalimantan indicates that the region may have hosted rainforest refugia during the ice age. Accordingly, analysis using DIY ABC software indicated that the Northeast and Central-West Kalimantan groups diverged 194 000 years ago. We conclude that global climate change during the Pleistocene strongly influenced the genetic diversity and structure of S. macrophylla populations in Kalimantan.