The present study examines the concurrent relationship between morphological awareness and vocabulary breadth and depth after accounting for the effect of other potential contributors. A sample of French-speaking fourth-grade children who spoke either French at home (L1) (n = 55) or another language (L2) (n = 85) completed a number of tests assessing vocabulary breadth, vocabulary depth, morphological awareness, phonological awareness, word reading fluency, word spelling, and nonverbal intelligence. The results showed that morphological awareness was strongly correlated with vocabulary breadth and depth for L1 and L2 participants. Moreover, hierarchical regression analyses indicated that after controlling for one dimension of vocabulary, phonological awareness, word reading fluency, word spelling, age and nonverbal intelligence, morphological awareness explained significant variance in the outcomes on the other dimension of vocabulary for L2 participants. However, the magnitude of the contribution of morphological awareness remained significant in the prediction of vocabulary depth for L1 children only. This paper highlights the implications for research and educational practice of our findings.