PURPOSE:This study examined the extent to which care-oriented attitudes and behaviours in adolescence (e.g., volunteering) predict positive development (PD; e.g., life satisfaction and meaning/purpose) in young adulthood (19-28 years). METHODS:The analytic sample comprised 1,359 participants participating from a 35-year (16 wave) population-based cohort study (The Australian Temperament Project). Adolescent care-oriented attitudes and behaviours were defined in mid-adolescence (15-16 years). Young adult PD was defined by latent growth curve modelling across three waves (19-20, 23-24, and 27-28 years). RESULTS:There was considerable variation in PD at the beginning of young adulthood (19-20 years) (variance of intercept = 40.22, SE = 4.53, p < .001). Once baseline PD levels were established in young adulthood, there was evidence of increasing PD over time (mean slope = .34, SE = .04, 95%CI = [.26, .41], p < .001, β = .65), with little variation in this rate of change between participants (variance of slope = .27, SE = .15, p = .087). After controlling for sex, parental education, and personality factors (b = 3.49, SE(b) = .67, 95%CI = [2.17, 4.80], p < .001, β = .22) care orientations in adolescence predicted PD at age 19-20 years, establishing the starting point of PD trajectories across young adulthood. CONCLUSIONS:Results suggest that promotion of care-oriented attitudes and behaviours in adolescence may enhance adult development by increasing PD levels at the start of the twenties. Intervening earlier in life is indicated as PD tends to remain stable throughout young adulthood once established.