Objective Personality dimensions are known to predict mortality and other health outcomes, but almost no research has assessed the effects of changes in personality traits on physical and mental health outcomes. In this article, we examined the effects of changes in the Big Five personality dimensions on health as assessed by the Short Form Health Survey (SF-36). Method Respondents were 11,105 Australian adults aged 2079 years (52.7% female). Latent difference score modeling was used to examine whether personality change over a 4-year period was associated with mental and physical health, and whether these effects were moderated by birth cohort. Results Increases in Conscientiousness and Extraversion were found to be associated with improved mental and physical health, whereas increased Neuroticism was linked with poorer health. The nature of these associations varied significantly by birth cohort. Conclusion The findings have implications for understanding how changes in personality traits over time are related to health, and could be used to aid the development of effective health promotion strategies targeted to specific personality traits and birth cohorts.