Research on multilingualism often assumes homogeneity within monolingual and multilingual groups, overlooking diversity in language environments, such as differences in language exposure and combinations. This study examines three such diversity indicators – language entropy, context entropy and linguistic distance – and their relationship to vocabulary in 4- to 5-year-old mono- and multilingual children (N = 257). Results reveal significantly greater vocabulary in monolinguals than multilinguals when comparing one language, but multilinguals outperform monolinguals on conceptual vocabulary. Vocabulary size in multilinguals showed a quadratic relationship with language and context entropy, initially increasing but declining at higher entropy levels. Additionally, children with greater linguistic distances generally had larger dominant vocabularies. However, within the group with high linguistic distance, further increased distance was linked to smaller dominant vocabularies. These findings suggest that the applied diversity indicators capture meaningful variation in language environments, offering valuable insights about diversity in environments on vocabulary outcomes in multilingual children.