Children are thought to learn second languages (L2s) using primarily implicit mechanisms, in contrast to adults, who primarily rely on explicit language learning. This difference is usually attributed to cognitive maturation, but adults also receive more explicit instruction than children, which may influence their learning strategies. This study crosses instruction condition with age, teaching forty children aged 5;3 to 7;11 and forty adults an artificial mini-language under implicit or explicit training conditions. Participants produced novel sentences and judged sentence grammaticality equally well in either condition, but both children and adults in the explicit training condition developed greater awareness of the mini-language’s structures – and greater awareness was associated with better performance for both age groups. Results show that explicit instruction affects children and adults in the same way, supporting the hypothesis that age differences in implicit vs. explicit L2 learning are not exclusively caused by maturation, but also influenced by instruction.