We study the lexical learning by children who have a genetic syndrome leading to mental retardation, the Down syndrome. Children with Down syndrome learn the names of new objects displayed in a scene. Our contribution explore to what extent the context associated with the object is beneficial or detrimental to the association between an object and its name in recall, production and a comprehension tasks. We assessed whether children with Down syndrome could learn four non-words associated with unfamiliar animals or musical instruments displayed in a scene (the context of presentation) and whether their performance would be influenced by the congruence of the context of presentation between the learning and the test phases. We hypothesized that the contextual congruence between the learning and the test will enhance children’s performance. In contrast, the association between an object and a new context in the test phase (compared to the association in the learning phase) would decrease performance. The results don’t confirm completely our hypothesis. There is no effect of context of presentation in recall and comprehension tasks. The effect of context of presentation is present only in denomination task. We compare this results with those of “normal” children. Consequences on lexical learning are discussed.