Cooperative problem solving with peers plays a central role in promoting children's cognitive and social development. This article reviews research on cooperative problem solving among preschool-age children in experimental settings and social play contexts. Studies suggest that cooperative interactions with peers in experimental settings are not as consistently beneficial to young children's cognitive growth as they are for school-age children. In contrast, both theory and empirical research suggest that social play like that seen in early childhood classrooms is a context in which young children gain critical knowledge from peer cooperation. However, these contexts differ in how much they allow children to create and sustain their own joint goals, which likely influences their learning from cooperative interactions in experimental settings. Features of cooperative social play that allow preschool children to create joint goals are considered, and suggestions for future research are proposed to integrate these features into experimental settings in order to provide a fuller understanding of the development of cooperative problem solving in young children and its benefits.