This study draws upon life course theory to examine the role that longitudinal exposure to changes in family income and family structure during childhood and adolescence plays in children’s academic achievement and mental health. Despite its contributions, prior research has been limited given its static approaches to family income and family structure and its inattention to the issue of time variability that induces time-varying confounding and overcontrolling. The present study extends the extant literature by identifying children’s longitudinal experience regarding family income and family structure and accounting for the temporal reciprocity between the two domains. To these ends, the analysis applies marginal structural models to data from the Korean Children & Youth Panel Survey 2010. Results show that longer exposure to low income and the experience of family structure transitions lowers children’s academic achievement throughout childhood and adolescence. In contrast, growing up in a single-parent family leads to a lower level of academic achievement and a higher level of depressive symptoms mainly during adolescence. These findings suggest that the effects of family income and family structure are co-existing rather than competing, and that the effects of each domain differ across early life stages.