Abstract: Objective: Personality is a potential factor determining individual differences in body-weight change. The current study examines associations between personality traits and change in body-mass index (BMI) over six years.Method: The participants were 762 women and 648 men aged 24–39years at the base-line. Personality was assessed with the Temperament and Character Inventory (TCI). For calculating BMI, height and weight were assessed at a clinic.Results: Longitudinal analyses conducted with linear regressions showed that in men and women, higher Novelty seeking predicted higher BMI (p<.05), whereas lower Reward dependence predicted higher BMI in women (p<.05) when baseline BMI was taken into account. In addition, cross-sectional associations for several TCI traits were found in age and education adjusted analyses. In women, higher Self transcendence (p<.05) was associated with higher BMI. In men, higher Novelty seeking (p<.001) and Self transcendence (p<.01) and lower Self directedness (p<.01) and Cooperativeness (p<.05) were associated with higher BMI. In addition, analyses of variance were conducted for multidimensional trait profiles (trait combinations). Significant temperament profile related differences in BMI were found in all analyses in women. Associations with character profiles and in men were less consistent.Conclusion: The results give support for personality playing a role in weight gain. Knowledge on personality may be used for motivating weight loss and designing weight management interventions.