Self-derivation of new factual knowledge through integration of separate episodes of learning is one means by which children build knowledge. Content generated in this manner becomes incorporated into the knowledge base and is retained over time; successful self-derivation predicts academic achievement. Yet the component processes on which self-derivation through integration depends are as yet unknown. In parallel studies with 6- and 8-year-olds (N = 41; Experiment 1) and 8- and 10-year-olds (N = 40; Experiment 2), we tested a number of predictors related to other productive processes and learning (reasoning, executive functions, verbal comprehension, and long-term retrieval). Across studies, with different methods, only verbal comprehension, a measure of accumulated semantic knowledge, accounted for unique variance in self-derivation through integration performance. The results indicate that self-derivation through integration of separate episodes relates to accumulation of knowledge and the ability to recruit the knowledge in the service of specific task demands. Implications for cognitive training and transfer are discussed.