This study synthesizes 79 standardized mean-change differences between control and treatment groups from 17 independent studies, investigating the effect of morphological interventions on literacy outcomes for students with literacy difficulties. Average total sample size ranged from 15 to 261 from a wide range of grade levels. Overall, morphological instruction showed a significant improvement on literacy achievement ([d-bar] = 0.33). Specifically, its effect was significant on several literacy outcomes such as phonological awareness ([d-bar] = 0.49), morphological awareness ([d-bar] = 0.40), vocabulary ([d-bar] = 0.40), reading comprehension ([d-bar] = 0.24), and spelling ([d-bar] = 0.20). Morphological instruction was particularly effective for children with reading, learning, or speech and language disabilities, English language learners, and struggling readers, suggesting the possibility that morphological instruction can remediate phonological processing challenges. Other moderators were also explored to explain differences in morphological intervention effects. These findings suggest students with literacy difficulties would benefit from morphological instruction.