Central to the study of invasive species is identifying source populations in their native ranges. Source populations of invasive species can provide important information about species life cycles, host use, and species-specific predators and parasites that could be deployed in a biological control program. The Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), is a serious invasive pest of urban forests in North America and Europe. We analyzed mitochondrial DNA haplotype frequencies and microsatellite allele frequencies to characterize phylogeographical patterns in potential source populations of A.. glabripennis. The data suggest that although there is evidence of genetic structure within and among populations in China, a substantial amount of genetic admixture has occurred. This admixture is probably due to recent reforestation efforts in China where beetles from previously isolated populations moved into new areas of abundant, susceptible, and stressed resources, leading to outbreak populations.