The jumping pitvipers of the genus Metlapilcoatlus are generally associated with montane environments and are widely distributed from central and southern Mexico to Panama. In this study, we analyzed the phylogenetic position and compared the morphology of a population from the Sierra Madre Oriental, within the Sierra Gorda Biosphere Reserve, to other species of jumping pitvipers. We implemented two mtDNA gene fragments (cyt b and ND4) of 50 specimens of the five Metlapilcoatlus species for phylogenetic reconstruction using Bayesian inference and maximum likelihood. We used a linear discriminant analysis and comparative statistics of external and hemipenial characters to assess the morphological differences among Metlapilcoatlus lineages. Our analyses support a strong genetic and morphological distinction of Metlapilcoatlus nummifer populations established to the north of the Trans-Mexican Volcanic Belt (Hidalgo, Northern Veracruz, and Querétaro) from other Metlapilcoatlus taxa. Based on this evidence we describe the populations from the north as a new species.