Macrolophus contains a small group of Palaearctic species with very simple and similar external morphology. The classification of these species has been based on variable characters such as body measurements, the height of the black band-shaped macula behind the eyes and the colour of the first antennal segment. Macrolophus melanotoma (Costa 1853), Macrolophus pygmaeus (Rambur 1839) and Macrolophus costalis Fieber 1858, are the most reputed predators of the genus. The classification history of M. melanotoma and M. pygmaeus shows a great number of misconceptions that have left the identity of the two species in confusion. Despite the economic importance of these two species, they have not received comprehensive taxonomical treatment until now. In this work, the morphological and sequence variation of a cytochrome b fragment (320 bp) were analysed to determine the identity of M. melanotoma and M. pygmaeus. Macrolophus costalis, Dicyphus cerastii Wagner 1951b, Dicyphus tamaninii Wagner 1951b, Cyrtopeltis geniculata Fieber 1861 and Nesidiocoris tenuis (Reuter 1895) were used as outgroup taxons in the phylogenetic analyses. Several evolutionary models were explored under a maximum likelihood framework. Macrolophus melanotoma and M. pygmaeus were classified as two distinct species based on monophyly, molecular and morphological data. Nodes at the species level were supported by high bootstrap values. M. pygmaeus and M. costalis are sister species, M. melanotoma basal to them. The shape of the black macula behind the eye may be used as a diagnostic character to differentiate M. melanotoma from M. pygmaeus with some degree of confidence.