We examined the relation of morphological awareness with language and literacy skills, namely phonological awareness, orthographic awareness, vocabulary, word reading, spelling, text reading fluency, and reading comprehension. We also examined potential moderators of the relations (grade level, orthographic depth of language, receptive vs. productive morphological awareness, inflectional vs. derivational vs. compound morphological awareness, and L1/L2 status). After systematic search, a total of 232 articles (965 unique samples, N = 49,936 participants, and 2,765 effect sizes in 17 languages) met inclusion criteria. Morphological awareness was, on average, moderately related to phonological awareness (r = 0.41), orthographic awareness (r = 0.39), vocabulary (r = 0.50), word reading (r = 0.49), spelling (r = 0.48), text reading fluency (r = 0.53), and reading comprehension (r = 0.54). Importantly, morphological awareness had a stronger relation with word reading in orthographically deep languages (0.52) than in orthographically shallow languages (0.38). The relation with vocabulary was stronger for upper elementary grades than for primary grades. The magnitude of the relation also varied by the nature of morphological awareness: productive morphological awareness had a stronger relation with phonological awareness and vocabulary than receptive morphological awareness; derivational morphological awareness had a stronger relation with vocabulary and word reading compared to inflectional morphological awareness; and compound morphological awareness had a weaker relation with phonological awareness but a stronger relation with vocabulary compared to inflectional morphological awareness. These results underscore the importance of morphological awareness in language and literacy skills, and reveal a nuanced and precise picture of their relations. [This is the online version of an article published in "Review of Educational Research."]