The aim of this prospective study was to examine the relations between organized activity involvement and internalizing and externalizing symptoms across four years of high school. Participants were 240 adolescents who varied in their risk for psychopathology. Information about adolescents’ activity involvement and internalizing and externalizing symptoms were provided by both self- and mother-reports. Structural equation modeling revealed that the prospective models fit the data well. In addition to showing that activity involvement and psychopathology were quite stable over the high school years, we found reciprocal effects for activity involvement and internalizing symptoms at some, although not all, time points. Specifically, controlling for prior symptoms and risk (i.e., maternal depression history), more activity involvement in tenth grade predicted fewer internalizing symptoms in eleventh grade, which then predicted more activity involvement in twelfth grade. No reciprocal relations were found for externalizing problems. These findings highlight the importance of examining internalizing symptoms as both a predictor and outcome of activity involvement during adolescence.