Some of Helicoverpa species (Noctuidae: Heliothinae) are among the worst Lepidopteran agricultural pests in the world, such as H. armigera, H. assulta, H. zea, and H. punctigera. Despite different distribution areas, these species possibly migrate long distances both with and without human transportation, mixing insecticide resistance alleles along the way. As these species are morphologically similar at the larval stage, diagnostic methods have been developed and utilized for their identification. Here, we developed a loop-mediated isothermal amplification (LAMP) assay for rapid and effective species diagnosis, along with PCR, to identify Korean field-collected or overseas samples. Species-specific primers were designed by aligning and comparing the mitochondrial genomes of related species, including four species. There are differences depending on the species and the optimal temperature and reaction time of the LAMP assay, depending on the set of four essential primers. For instance, H. armigera sensitivity is good enough to allow visual discrimination when reacted at 61°C for 30 minutes. This simple and accurate LAMP assay can be used for intensive field monitoring and integrated management of these species.