This study assessed the status of te reo Māori, the indigenous language of New Zealand, in the context of New Zealand English. From a broadly representative sample of 6327 two-year-olds (Growing Up in New Zealand), 6090 mothers (96%) reported their children understood English, and 763 mothers (12%) reported their children understood Māori. Parents completed the new MacArthur-Bates Communicative Development Inventory short forms for te reo Māori (NZM: CDI sf) and New Zealand English (NZE: CDI sf). Mothers with higher education levels had children with larger vocabularies in both te reo Māori and NZ English. For English speakers, vocabulary advantages also existed for girls, first-borns, monolinguals, those living in areas of lower deprivation, and those whose mothers had no concerns about their speech and language. Because more than 99% of Māori speakers were bilingual, te reo Māori acquisition appears to be occurring in the context of the acquisition of New Zealand English.