Children live in a dynamic environment, in which objects continually change locations and move into and out of occlusion. Children must therefore rely on working memory to store information from the environment and to update those stored representations as the environment changes. Previous work suggests that the ability to store information in working memory increases through infancy and childhood. However, less is known about the development of the ability to update stored information. Participants were 63 4-7-year-old children (37 girls; 34 caregivers completed optional demographic forms, and those children were reported as Asian [one], Asian/White [four], Black [one], Middle East/Arab [one], or White [27]; two were Hispanic/Latinx). We asked children to keep track of arrays of hidden items that either remained where they were hidden (static trials) or swapped locations (swap trials) and then to identify from two alternatives which item was hidden in a particular location. We manipulated the number of items in the arrays and the number of times the items swapped locations in order to investigate how increasing storage and updating load impacted children's performance. We found that children's ability to update working memory developed significantly across our age range. Updating appeared to impose a significant one-time cost to working memory performance, regardless of the number of times items swapped. Our results yield new insights into the developmental trajectories of storage and updating in working memory across early childhood.