Morphological variation can be promoted by ecological factors and the evolutionary history of the taxa. The Aspidoscelis gularis complex is one of the groups of whiptail lizards that exhibits one of the widest distributions in North America, occupying a great variety of environments. Its members are similar in morphology, which has contributed to the taxonomic uncertainty in the group. In this study, variation in size and head shape was analysed considering a phylogenetic hypothesis based on the Cytb and ND2 mitochondrial genes. Six evolutionarily significant units were found, of which the morphological patterns were analysed. Eleven morphological characters and two landmark configurations of the head were used. Analysis of size revealed a pattern of sexual dimorphism, while geometric morphometrics suggested that there is no dimorphism in head shape. Neither size nor shape shows unique patterns of morphological variation between the evolutionarily significant units, which could be attributed to morphological conservatism and recurrent hybridization in whiptails.