Insects are rich in proteins and could be an alternative source of macronutrients to feed animals and humans. Over the past few years, numerous companies have started producing insects for feed purposes. In Europe, the processed animal proteins obtained from seven insect species have been authorised for aquaculture by Commission Regulation (EU) 2017/893 since 1 July 2017. Methods of authentication are required to check the conformity of the products. In this study, we propose a real-time PCR method for the specific detection of the black soldier fly (Hermetia illucens L.), one of the most widely used insects for feed production. The developed PCR assays amplify a 67 bp fragment based on the mitochondrial COX3 gene coding for subunit 3 of the cytochrome c oxidase. The qualitative method was tested according to several performance criteria. The specificity was tested against 51 insect species. The specificity was also checked against plant species and other animal species such as crustaceans, mammals and birds. The sensitivity, efficiency and robustness of the PCR test were successfully tested. The applicability of the test was proven through the analysis of real-life processed samples (industrial meals) of H. illucens.