The invasive black soldier fly, Hermetia illucens, has been paid much attention as an excellent organic matter decomposer. We conducted the nationwide survey and the population genetic study using a mitochondrial cytochrome C oxidase 1 gene to understand its genetic diversity and distribution pattern in Korea. The results show that it has successfully settled down in South Korea and there are only 10 haplotypes and the populations of the insect are highly differentiated. The results indicate that only few maternal lineages were introduced and their dispersal was restrained due to their short distance flying tendency since their introduction.