In young adults, sleeping after learning has been shown to facilitate relearning and long-term retention, compared to staying awake (Mazza et al., in revision). Children (aged 8) and elderly people (aged 71) learned Swahili-French word pairs to criterion during a learning session taking place in the morning or evening (Wake and Sleep group, respectively). Participants spent 12 hours filled with wakefulness or a night of sleep, then performed a relearning session to criterion either in the evening (Wake) or the following morning (Sleep). One week later, retention was tested. Sleep appeared to affect memory differently according to age. The groups of children did not differ during the relearning session whereas the Sleep outperformed the Wake group after one week. In elderly participants, no effect of sleep was observed. Thus, the enhancing effect of sleep is most pronounced in adults, moderate in children, and weak in elderly people.