Adolescents' academic achievement is closely associated with their future time perspective. However, the reciprocal nature of this relationship remains ambiguous due to a lack of longitudinal studies. This study investigated the developmental trajectories of future time perspective and academic achievement among adolescents, as well as reciprocal relations between future time perspective and academic achievement. Between 2017 and 2019, we collected 373 adolescents' (baseline Mage = 14.48, SD = 1.90; 49% girls) future time perspective and academic achievement four times from Henan and Hunan Province, China. Each is separated by a 6-month interval. Chinese adolescents' future time perspective was relatively stable. Regarding academic achievement, two distinct developmental trajectories of academic achievement were identified (i.e., high positive growth class and low negative growth class). Those who excel tended to experience an upward trajectory, while those with poorer grades continued to experience a downward trajectory. In the high positive growth class, the intercept of future time perspective was positively correlated with the rate of academic achievement growth, whereas, in the low negative growth class, it negatively predicted the rate of academic achievement decline. More importantly, reciprocal relations existed between future time perspective and academic achievement. Adolescents' future time perspective may serve as a protective factor for academic achievement, while high academic achievement may also benefit future time perspective. Interventions to enhance academic achievement should prioritize cultivating adolescents' future perspectives. Additionally, preventing the adverse consequences of subpar academic achievement on future time perspective is imperative.