The diamondback moth, Plutella xylostella, is one of the most economically important agricultural pests. The larvae of this moth cause damage by feeding on the foliage of cruciferous vegetables such as cabbage, broccoli, cauliflower and rapeseed. Control generally comprises chemical treatment; however, the diamondback moth is renowned for rapid development of resistance to pesticides. Other methods, such as biological control, have not been able to provide adequate protection. Germline transformation of pest insects has become available in recent years as an enabling technology for new genetics-based control methods, such as the Release of Insects carrying a Dominant Lethal (RIDL®). In the present study, we report the first transformation of the diamondback moth, using the piggyBac transposable element, by embryo microinjection. In generating transgenic strains using four different constructs, the function of three regulatory sequences in this moth was demonstrated in driving expression of fluorescent proteins. The transformation rates achieved, 0.48–0.68%, are relatively low compared with those described in other Lepidoptera, but not prohibitive, and are likely to increase with experience. We anticipate that germline transformation of the diamondback moth will permit the development of RIDL strains for use against this pest and facilitate the wider use of this species as a model organism for basic studies.