Contemporary youth spend increasingly longer time in the educational system, where their career pursuits become closely intertwined with their educational goals. As career development is a life-long process, adolescents start working on their careers long before they engage in actual work behaviors. Therefore, in order for school to adaptively prepare youth for their future work lives, career adaptability and academic achievement should be reciprocally and positively linked throughout adolescence. To date, more longitudinal proof for these relations is needed. To address this shortcoming, we investigated cross-lagged associations between these two constructs in a three-wave longitudinal study, testing the moderating role of adolescents' gender, school type, and age. Participants were 1151 adolescents (41.3% boys), who completed the same paper-and-pencil measure three times across an academic year. Results showed positive reciprocal associations between career concern and academic achievement (i.e., Grand Point Average). This indicates that adolescents with a strong future orientation, who were already invested in career planning activities tended to perform better in school and vice-versa, high academic achievement further strengthened adolescents' positive outlooks on their vocational future. We also detected positive unidirectional links from academic achievement to career control and career confidence across one academic year. Interestingly, we did not find significant longitudinal links between career curiosity and academic achievement. These patterns of longitudinal relations applied equally to boys and girls, to those attending university-preparatory and work-bound schools, and to early-to-middle and middle-to-late adolescents. Research and applied implications of these findings are detailed.