The genus Pergamasus currently comprises 57 valid species of large epigeic predatory mites, predominantly distributed in Europe. Despite their relatively large body size and the apparent ease of observing diagnostic characters, species-level identification remains challenging. In addition to other factors, taxonomic work is complicated by the high degree of morphological uniformity among many species, with interspecific differences often being subtle and inconspicuous. This difficulty is further exacerbated by pronounced intraspecific variability in diagnostic characters, particularly in morphologically similar species. For these reasons, we conducted a comprehensive analysis of both morphological and molecular characters of species within the genus Pergamasus, with special emphasis on those species groups considered most problematic from an identification perspective, especially the crassipes species group. Material from several European countries was examined. Freshly collected material as well as specimens deposited at the Department of Zoology of Comenius University were used for morphological analyses, molecular analyses were based exclusively on freshly collected specimens. DNA was isolated using the QIAGEN DNeasy kit, and the COI gene and ITS region were sequenced. All specimens were mounted as permanent slides and examined under a light microscope. Species from all three subgenera of Pergamasus were analyzed, with the primary focus on the crassipes species group. Notably, Pergamasus crassipes has traditionally been considered a widespread and highly abundant species across Europe, possibly the most common species of the genus. However, this assumption holds only until the material is examined in detail. For example, a revision of material (over 1,000 specimens) from Slovakia identified and partly published as P. crassipes did not confirm the presence of this species in the country. Most specimens were misidentified individuals of Pergamasus primorellus, and exceptionally of Pergamasus longicornis. Based on these findings, we conclude that all historical distribution data attributed to P. crassipes should be interpreted as referring to the crassipes species group rather than to the species P. crassipes sensu stricto. Furthermore, using an integrative approach combining morphological and molecular data, we discuss relationships within the crassipes species group, with particular emphasis on morphological characters that we consider most reliable for species identification. The diagnostic characters identified in this study provide a practical basis for improving species identification within the genus Pergamasus. The research was supported by the grant agency VEGA, with the grant number 1/0702/23.