Mother-child planning was examined in relation to child emotional functioning and first-grade school performance. Ninety dyads were randomly assigned to the explicit-goal condition (emphasized accuracy and preparation for a child-only posttest) or the no-explicit-goal condition (dyads just asked to work together). In the no-explicit-goal condition only, children higher in negative emotionality and lower in regulation skills were less engaged in the task and planned less effectively. Both mother-child planning and adaptive child emotional functioning were positively associated with school performance. Results suggest that child emotional functioning mediated associations between planning and school performance. Implications of these findings for the development of planning and children's transition to school are discussed.