The aim of the present study was to empirically disentangle the interdependencies of the impact of nonverbal intelligence, working memory capacities, and phonological processing skills on early reading decoding and spelling within a latent variable approach. In a sample of 127 children, these cognitive preconditions were assessed before the onset of formal education, whereas reading as well as spelling achievement was measured at the end of grade 1. The findings indicate that working memory does contribute to the prediction of early reading and spelling, and that this contribution outperforms that of general intelligence and phonological recoding from long-term memory during the early steps of reading and spelling acquisition. Moreover, the results show that phonological awareness mediates the effects of working memory capacities on early literacy outcomes. The role of working memory and phonological awareness as key cognitive preconditions of early reading and spelling are discussed.