Studies of early vocabulary acquisition, such as whether nouns or verbs are easier to learn, and at what stage children acquire closed-class words have produced conflicting results, both within and across languages. Studying vocabulary development in Irish can contribute to this debate, as it could be considered to have verb-highlighting features, including a VSO word order, single-word sentences comprised of a verb marked only for person and has relatively simpler morphological marking on verbs than nouns. In addition, Irish as has a semantically rich system of grammatical lexemes, particularly for prepositions and pronouns. This study adapted a parent-report assessment to Irish, and measured vocabulary development longitudinally for children aged between 16 and 40 months. The findings indicated that despite predictions that verbs would be acquired earlier, the children had a strong preference for nouns. On the other hand, closed-class words were acquired when the Irish-speaking children had relatively smaller vocabulary sizes compared to children acquiring other languages. Possible reasons for these findings will be explored, including morphological and semantic features of Irish, as well as aspects such as frequency, saliency and pragmatic functions of the input language. The results will be related to crosslinguistic studies of early lexical acquisition from parent report.