This research brings new evidence on early lexical acquisition in Wichi, an under-studied indigenous language in which verbs occupy a privileged position in the input and in conjunction with nouns are characterized by a complex and rich morphology. Focusing on infants ranging from one- to three-year-olds, we analyzed the parental report of infants' vocabulary (Study 1) and naturalistic speech samples of children and their caregivers (Study 2). Results reveal that: (1) although verbs predominate in the linguistic input, children's lexicons favor nouns over verbs; (2) children's early noun-advantage decreases, coming into closer alignment with the patterns in the linguistic input at a MLU of 1.5; and (3) this early transition is temporally related to children's increasing productive command over the grammatical categories that characterize the morphology of both nouns and verbs. These findings emphasize the early effects of language-specific properties of the input, broadening the vantage point from which to view the lexical acquisition process.