In this chapter, we first review several cognitive explanations for age effects in second (L2) language learning, particularly those that relate to different aspects of human memory. We then report the results of a study that compares the performance of age-matched groups of children and adults (native speakers and L2 learners) on explicit and implicit tests of memory of English words read under two conditions (story vs. list). Overall, the obtained findings showed no essential differences in memory performance between 11–13-year-old children and 17–26-year-old adults learning English as their L2. More strikingly, the L2 learners’ performance on tests of explicit and implicit memory was very similar to the performance of age-matched native English-speaking children and adults. We discuss contributions of explicit and implicit memory to child–adult differences in L2 learning.