In the present work we conduct a comparative study of the cranial and dental samples of the early machairodontine Machairodus aphanistus from the Vallesian (MN 10) sites of Batallones-1 and Batallones-3 (Torrejón de Velasco, Madrid, Spain). These sites, which have yielded the most abundant and complete samples of this felid, show interesting differences in faunal composition and age, thus providing a unique opportunity for both qualitative and quantitative comparisons between two populations of the same species. The study reveals differences in a number of cranial features, and statistically significant differences in teeth size and proportions. Although probably not enough to support a separation at the species level, these observations fit well with the morphological evolution of the lineage leading towards more derived forms such as the Turolian Amphimachairodus giganteus.