Purpose: The main goal of this study was to examine whether the morphological structure of a child's first language determined the strength of association between morphological awareness and reading and spelling skills in English, their second language. Methods: The sample consisted of 888 Grade six students who had English as their first language and 244 English Language Learners (ELLs) who came from seven home language backgrounds: Chinese, Filipino, Germanic, Korean, Persian, Romance, and Slavic. Participants were given a series of standardized tests for word reading, reading comprehension, and spelling, and experimental measures of morphological, phonological, and syntactic awareness, as well as reading fluency and reading comprehension. Results: The results revealed that children in the ELL groups differed from the English monolingual group mostly on the oral language tasks, but their reading skills were high and equivalent to those of the monolingual group. Moreover, it was confirmed that morphological awareness is important for all aspects of reading and spelling, and its influence is independent of that of phonological awareness and syntactic awareness. Conclusion: The associations between morphological awareness and reading and spelling in a second language seem to be influenced by the morphological structure of the home language, such that the association was stronger for children whose home languages were morphologically transparent.