The use of a verbal rehearsal strategy (repeating the items to be remembered to oneself in serial order) has been identified as a key factor in explaining working memory (WM) development. However, the debate remains open with regard to the age at which children are able to use it, and the actual benefits of using such a strategy. Numerous methodological constraints to identify WM strategies limit the interpretation of current findings reported in the literature. Moreover, the sequential nature of the cumulative rehearsal strategy means that its use may have a particular influence on maintaining serial order information. The present study aimed to examine: (1) whether children aged 4, 5, and 6 (n = 74, 39 female, n = 61, 29 female, and n = 72, 29 female, respectively) were able to implement an instructed verbal rehearsal strategy; and (2) the benefits of using such a strategy in terms of WM performance. Specifically, we invited children to use cumulative rehearsal, naming (simple rehearsal), or no strategy when performing verbal WM tasks (immediate serial recall and item and order serial recognition). Moreover, the specific influence of instructed strategies on item and serial order maintenance was assessed in the different age groups. While the benefits of using the naming strategy were limited, cumulative rehearsal instruction increased WM performance in all age groups, particularly for serial order information. Our results demonstrate that, as early as 4 years old, children were able to implement, and benefit from a short period of cumulative rehearsal instruction.