Agonopterix assimilella is a moth of the Depressariidae family. It is found in most of Europe. The wingspan is 15–21 mm. Adults are on wing from April to June. The larvae feed on Cytisus scoparius. They initially feed inside the stems, but later feed externally between two green stems sewn together in parallel. Larvae can be found from October to February. The species overwinters in the larval stage within the stem.