A preliminary phylogenetic reconstruction of the Dondice nudibranch genus, based on an integrative taxonomical approach, was explored and relationships occurring among other correlated genera were determined. Phylogenetic analyses with the mostly used markers in nudibranchs, the nuclear H3 gene and the two mitochondrial 16S rDNA and COI were integrated with information from anatomical analyses. The Mediterranean nudibranch diversity has yet to be thoroughly studied since new species are constantly discovered and some cryptic species identified only by recent molecular approaches. In the frame of this phylogenetic study, Dondice trainitoi sp. nov. is here described based on specimens collected from the central Tyrrhenian Sea (Mediterranean Sea). Morphological, anatomical and molecular analyses were carried out to assess the diagnostic characters of this new taxon, and to compare them with those of the other members of the genus.