Extensive evidence indicates that early vocabulary skills predict later reading development among monolingually developing children. Some evidence suggests that a relationship between vocabulary and later reading also holds across languages among children whose home language differs from the school language. However, these findings have been mixed and it remains unclear if, and under what circumstances, vocabulary in one language supports reading comprehension development in another. The present study followed 84 Spanish-English bilingual children, assessing their vocabulary skills at 5 years and their reading comprehension at 6, 7, 8, and 9 years. Longitudinal multilevel models revealed significant within-language relations between early vocabulary knowledge and subsequent reading comprehension in both English and Spanish and no across-language relations. There were significant concurrent across-language relations between English and Spanish reading comprehension skills. These findings suggest that the contribution of vocabulary knowledge to reading comprehension is language specific but that there are also language general components to reading comprehension, which result in significant concurrent relations between reading comprehension skill across languages.