This study explored the role of early oral language in reading development among adult heritage language (HL) learners to provide insights into the possible developmental pattern of HL reading development. One hundred and ninety-five English-speaking Chinese HL (CHL) students participated in this study. They completed a language background survey pertaining to their early language use in different social contexts and a series of measurements including oral vocabulary knowledge, print vocabulary knowledge, morphological awareness, lexical inferencing ability, and reading comprehension. Drawing upon multivariate path analysis, the study found that oral vocabulary knowledge, as an indicator of the benefit stemming from oral language experiences, contributed to print vocabulary knowledge and morphological awareness directly. However, there was no significant direct effect of oral vocabulary knowledge on higher-level reading skills (lexical inference and reading comprehension). As well, oral vocabulary contributed to higher-level reading skills only through the mediation of word-knowledge skills (print vocabulary and morphological awareness). The results suggest that oral language capacity (indexed by oral vocabulary knowledge) alone is insufficient for higher-level reading ability, but it serves as an intermediary resource to enhance higher-level inferencing and comprehension abilities among HL students. Pedagogical implications were provided to inform HL reading instruction based on the multiple diversities of HL language experiences.