This paper compares the acquisition of verb morphology in five Mayan languages, using a comparative method based on historical linguistics to establish precise equivalences between linguistic categories in the five languages. Earlier work on the acquisition of these languages, based on examination of longitudinal samples of naturally-occuring child language, established that in some of the languages (Tzeltal, Tzotzil) bare roots were the predominant forms for children’s early verbs, but in three other languages (Yukatek, K’iche’, Q’anjobal) unanalyzed portions of the final part of the verb were more likely. That is, children acquiring different Mayan languages initially produce different parts of the adult verb forms. In this paper we analyse the structures of verbs in caregiver speech to these same children, using samples from two-year-old children and their caregivers, and assess the degree to which features of the input might account for the children’s early verb forms in these five Mayan languages. We found that the frequency with which adults produce verbal roots at the extreme right of words and sentences influences the frequency with which children produce bare verb roots in their early verb expressions, while production of verb roots at the extreme left does not, suggesting that the children ignore the extreme left of verbs and sentences when extracting verb roots.