Morphological awareness (MA) was defined as “awareness of morphemic structures of words and the ability to reflect on and manipulate that structure” (Carlisle, 1995, p.194). MA is viewed as a multi-faceted construct, including aspects like inflectional, derivational and compounding morphology. It has been identified as a crucial metalinguistic awareness influencing children’s literacy outcomes. Though a growing body of evidence has shown positive the effects of MA instructions, it remains relatively unclear regarding what components of MA instructions uniquely contribute to literacy outcomes. This study adopted randomized controlled trial design and examined the effects of English morphological instructions on improving word reading, reading comprehension and spelling skills in 29 Hong Kong Chinese third graders who speak English as a second language. Students were randomly assigned into three groups: a) derivational morphology group (n = 10), b) compounding morphology plus derivational morphology group (n = 10) or c) business-as-usual group (n = 9). All children received intervention for 8 hours (two 30-min sessions per week for 8 weeks) and were administered a battery of linguistic and cognitive tasks, including non-verbal intelligence, inflectional, derivational and compounding morphology, vocabulary, word reading, spelling skills and reading comprehension at pretest and posttest. The results of the study would be discussed in the presentation. The findings may shed light on the causal role of morphological awareness on literacy development as well as the optimal manner in teaching morphological awareness. Copyright © 2020 ARWA.