This study examined the role of parents' early home language use in the English reading development of emergent bilinguals (N = 3,058) and how their relations are moderated by children's oral English language proficiency using longitudinal data from kindergarten to eighth grade (ages 6-15 years). Results from multi-group latent basis growth models indicated that emergent bilinguals whose parents used a non-English (native) language more frequently at home when they were in kindergarten started with lower English reading achievement but made greater growth compared to children whose parents used their native language less frequently. Consequently, the effects of parents' non-English language use on English reading achievement dissipated by eighth grade. This growth pattern was more prominent for emergent bilinguals with initially limited English proficiency than for emergent bilinguals with fluent English proficiency. The analyses of reading subskills suggest this pattern is primarily attributable to the delayed English reading acquisition of emergent bilinguals with limited English proficiency in constrained reading skills (Word Reading, Reading Words in Context). Our findings suggest that parents' frequent native language use neither has facilitative effects on English language use nor does it hamper emergent bilinguals' long-term English reading development.