Sleep behaviour is correlated and causally related to physical and mental health. Limited longitudinal data exist on the associations of poor sleep behaviour in childhood and adolescence with adult health. Parent-reported sleep behaviours from 1993 participants of the Raine Study (at ages 5, 8, 10, 14, 17) were used to determine sleep trajectories (using latent class growth analysis). Measures of physical and mental health were compared between sleep trajectories using generalised linear models (at age 20). Three sleep trajectories were identified as follows: 43% of participants belonged to a trajectory with 'consistently minimal' sleep problems, 49% showed some 'declining' in reporting of sleep problems incidence and 8% had 'persistent' sleep problems. Participants in the 'consistently minimal' trajectory had better physical and mental health outcomes at age 20 compared to those in the 'declining' and 'persistent' trajectories. For example, 'consistently minimal' participants had significantly lower body fat percentage (mean difference: -3.89% (95% CI: -7.41 to -0.38)) and a higher (better) SF-12 mental component score (mean difference: 4.78 (95% CI: 2.35-7.21)) compared to participants in the 'persistent' trajectory. Poor sleep behaviour across childhood and adolescent years is related to poorer physical and mental health in young adulthood.