Preterm-born individuals are at risk for poorer executive functions. Longitudinal studies investigating whether preterm-born individuals present persistent cognitive deficits, or a transient delay of development are scarce. We assessed developmental trajectories of executive functions (inhibition, working memory, cognitive flexibility) in 29 very preterm-born individuals (<32 weeks' gestation) and 25 term-born controls longitudinally over two time points, namely in childhood (7-12 years of age, TP1) and adolescence (13-16 years of age, TP2). Individual changes in executive functions were examined using relative difference scores (TP2 - TP1) / TP1). There was a significantly stronger improvement of inhibition (U = 477, p = .024) and cognitive flexibility (U = 312, p = .029) between childhood and adolescence in very preterm-born individuals than in term-born controls. Preterm-born individuals improved their performance in the domain of cognitive flexibility significantly more often (76%) between childhood and adolescence than controls (31%, χ2 = 8.6, p = .003). Controls worsened significantly more often (36%) in the domain of inhibition than the preterm group (14%, χ2 = 4.8, p = .028). Results indicate that healthy preterm-born individuals show prolonged development of executive functions throughout childhood up into adolescence.