The NLSY97 data were used to explore the patterns of developmental trajectories of body weight in adolescence and how they affected the likelihood of college completion in young adulthood among 2,275 youths aged 13 and 14 in Wave 1. A strong weight trajectory gradient was found for rates of college completion. The study further explored the role of non-cognitive traits in the association between weight trajectories and college attainment. Non-cognitive traits were found to partially mediate the impact of certain weight trajectories on the likelihood of college completion. Some moderating effects of conscientiousness were also found. The findings from the gender and weight trajectory interaction terms showed that a stronger negative impact of weight trajectory on college completion is only observed for women in the late-teen-onset overweight group. This study highlights the importance of using a longitudinal weight measure and the role of non-cognitive traits in adolescent obesity research.