Lycorma delicatula (White) was identified in 2004 as an invasive pest in South Korea, where it causes serious damage to vineyard crops. To investigate the population structure and dispersal pattern of L. delicatula in South Korea, we estimated the population genetic structure and gene flow among nine locations across the country using seven microsatellite markers. Although L. delicatula spread throughout most of its geographical range in South Korea within 5–7 years following invasion, its populations show evidence of genetic structuring across the range with a low but significant global FST (genetic differentiation across all populations) of 0.0474. Bayesian-based clustering analysis indicates the presence of at least three genetically unique populations in South Korea, including populations in northeastern South Korea, which show a distinct genetic background. However, isolation by distance suggests that populations in South Korea have not yet reached genetic equilibrium. Estimates of the historical rate of gene flow (Nem) indicate that relatively high rates of flow have been maintained among populations within the western region, which may indicate recent range expansion. A population assignment test using the first-generation migrant detection method suggested that long-distance dispersal of L. delicatula may have occurred over large areas of South Korea. More complex dispersal patterns may have occurred during L. delicatula invasion of heterogeneous landscapes in South Korea.