This study examined the relationship between phonological and morphological awareness in kindergarten, and their respective influence on learning to read in first grade, through an experimental training design with three groups of children. One experimental group received phonological awareness training while the other received morphological awareness training. The control group did not receive any training. Both training sessions were efficient since the largest pre- and post-test improvements were observed in the trained domains. Reciprocal influence analysis indicated that morphological awareness improved phonological sensitivity, but not the explicit manipulation of phonemes. In addition, phonological awareness training helped children to segment morphemes, but not to derive complex words. Thus, while some processes are shared by both metalinguistic domains, each domain appears to have its own specificity and may develop independently, at least partly. Even though morphological awareness training was found to be efficient at the kindergarten level, no clear impact on reading was found at the first-grade level, while phonological training displayed a clear positive effect on reading.