This study examined the relationship between morphological awareness and reading comprehension in English among Spanish-speaking English language learners (ELLs) followed from fourth through fifth grade. Students' ability to decompose derived words while reading was assessed using an experimental task. Multiple regression analyses were used to investigate the contribution of performance on this task to reading comprehension above and beyond word reading skills, phonological awareness, and breadth of vocabulary knowledge. The relationship between morphological awareness and reading comprehension was found to strengthen between fourth and fifth grade, and in fifth grade, morphological awareness was found to be a significant predictor of reading comprehension. The findings were robust across two measures of reading comprehension and two methods of scoring the experimental task of morphological awareness, and thus support the inclusion of derivational morphology in a model of the English reading comprehension of Spanish-speaking ELLs.