Moths in the family Gracillariidae constitute one of the primary groups of plant-mining microlepidoptera. While the majority of species are leaf miners, the family shows a diversity of other life-history strategies, such as fruit mining, stem mining, leaf rolling, boring, and galling. Many species are highly invasive and serious pests of agricultural and ornamental plants. Gracillariids include 1855 described species of which 257 have been recorded in Europe. Here we present barcode data for more than 2000 specimens for 230 species representing 89.5% of the European fauna. On average seven specimens were barcoded per species. Morphology and DNA barcodes were carefully studied and compared. Preliminary results show that barcoding is capable of unambiguously discriminating ~97% of the species investigated so far, including some of closely related species notoriously difficult to identify. We highlight some interesting cases of barcode similarity, barcode sharing, and deep intraspecific splits. DNA barcoding revealed divergent clusters within several described species when extending the study area to the whole continent of Europe calling attention for closer taxonomic scrutiny. Our comprehensive DNA barcode library for Gracillariidae leaf-mining micromoths will make identification more straightforward in particular larvae and light trapped specimens for which no host plant data is known. This research highlights the importance of international cooperation among European entomologists to complete the barcoding of all the Lepidoptera of Europe.