Adolescence is a period of social, psychological and biological development. During adolescence, relationships with others become more complex, peer relationships are paramount and social cognition develops substantially. These psychosocial changes are paralleled by structural and functional changes in the brain. Existing research in adolescent neurocognitive development has focused largely on averages, but this obscures meaningful individual variation in development. In this Perspective, we propose that the field should now move toward studying individual differences. We start by discussing individual variation in structural and functional brain development. To illustrate the importance of considering individual differences in development, we consider three sources of variation that contribute to neurocognitive processing: socioeconomic status, culture and peer environment. To assess individual differences in neurodevelopmental trajectories, large-scale longitudinal datasets are required. Future developmental neuroimaging studies should attempt to characterize individual differences to move toward a more nuanced understanding of neurocognitive changes during adolescence.