Age-related changes in mental flexibility, in the form of task switching, were assessed in 292 children (58-156 months old). Task switching was examined with a new task for young children, the Switch Task for Children (STC). The STC consists of two easy, comparable games and does not require reading skills, which makes it suitable for children younger than 6 years of age. The aims of the present study were: (1) to evaluate the STC; (2) to examine task switching in Young children; and (3) to study age-related changes in task switching across childhood. The results indicated that children younger than 6 years are able to switch between two tasks and that general performance increased with age. Young children (58-89 months) displayed a larger global switch cost, that is they made more errors when the tasks were presented randomly compared with a repeated-task baseline, than older children (106-156 months). These findings suggest that the STC is a useful task for detecting task-switching abilities in young children and that the ability to maintain and manipulate two different tasks in working memory, is present, but not yet fully developed, in young children.