Identifying alien species is important to detect invaders early and to survey shifts in species ranges in the context of global change. Here we present the first recorded occurrences of the Mediterranean digger wasp Psenulus fulvicornis (Schenck, 1857) (Crabronidae) in Switzerland. To aid species identification and separation from the morphologically similar congener P. schencki (Tournier, 1889), which is known to occur in Switzerland, we show discriminating morphological characters and deliver the first DNA barcode sequences and a molecular phylogenetic tree of the mitochondrial cox1 locus from specimens sampled at the European scale. While the species can be readily separated by morphological characters, maximum likelihood and Bayesian inferred phylogenetic trees revealed the existence of polyphyly. Thus, we could not identify a barcoding gap at the European scale, which may hamper taxon identification. Nevertheless, cox1 sequences were diagnostic for all Central European specimens. Finally, an exhaustive revision of P. schencki accessions in the Swiss historical museum and private collections did not reveal overlooked specimens of P. fulvicornis. This confirms the status of P. fulvicornis as a new species to Switzerland, where it is currently only known from the Cantons of Zurich and Geneva; inhabiting warm lowland habitats such as urban gardens.