Abstract.— The black soldier fly, Hermetia illucens, has the potential to reduce animal waste on livestock facilities and produce an animal‐grade feedstuff high in protein and fat. The lipid content of insects is largely dependent on their diet. Data from this study suggest that black soldier fly prepupae incorporate α‐linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) when fish offal is included in their diet. Fly larvae were fed three different proportions of fish offal and cow manure diets over a 21‐d trial. An additional group of larvae were fed 22% fish offal diet within 24 h of their pupation. Larvae fed fish offal were, on average, 30% lipid, which was 43% more than the controls fed cow manure only, and approximately 3% of this lipid was omega‐3 fatty acids (EPA, DHA, and ALA). Furthermore, this concentration of omega‐3 fatty acids was achieved within 24 h of feeding fish offal. These omega‐3 fatty‐acid‐enhanced prepupae may be a suitable fish meal and fish oil replacement for carnivorous fish and other animal diets. In addition, they may provide a method of reducing and recycling fish offal from processing plants.