Objective: To examine the association between personality traits, defined by the Five-Factor Model, and the initiation and termination of physical activity across adulthood. Design: Longitudinal analysis of participants from nine samples (N > 28,000). Main outcome measures: Physical activity status at follow-up. Results: A random-effect meta-analysis revealed that higher conscientiousness, extraversion, and openness were related to a higher likelihood of initiation of physical activity over time among individuals who were physically inactive at baseline and to a lower risk of termination of physical activity among those who were physically active at baseline. In contrast, higher neuroticism was associated with a lower probability of initiation of physical activity and a higher likelihood of termination over time. Although not hypothesised, agreeableness was also associated with better physical activity outcomes over time. Conclusion: This study provides the largest and the longest evidence of a replicable association between personality and change in physical activity status. Personality may motivate both the initiation and termination of physical activity.