The purpose of the present study was to explore the dimensionality of the English home language and literacy environment (HLLE) construct in multilingual home settings for fourth- and fifth-grade emergent bilinguals. The authors also evaluated a framework of mediating mechanisms underlying the effects of emergent bilinguals' English HLLE on English reading comprehension by testing the mediation role of morphological awareness and vocabulary. Confirmatory factor analytic results showed that home language use and home literacy environment are two distinct but internally related subdomains embedded within the general HLLE construct. This finding confirms the complex and multifaceted nature of HLLE as depicted in the literature. Moreover, findings from sequential mediation analyses indicated that HLLE had no significant direct effect on English reading comprehension but made a substantial contribution to morphological awareness, which in turn influenced vocabulary and further enhanced reading comprehension. The present study contributes to the current literature by providing a more comprehensive view of the pathways through which emergent bilinguals' HLLE leads to reading comprehension.