Objective Previous research has found that conscientiousness has positive associations with preventative health‐related behaviors and self‐perceived health, but little is known about the links between changes in these variables over time. In the present study, we examined how levels and changes in conscientiousness were linked to levels and changes in both preventative health‐related behaviors and self‐perceived physical health. Method Personality and health questionnaires were administered to participants in two waves, with an interval of approximately three years. Participants ranged in age from 19 to 94. To elucidate the tripartite relations between conscientiousness, preventative health‐related behaviors, and self‐perceived physical health, we used latent change models to estimate levels and changes of these latent constructs over time. Results Changes in conscientiousness were significantly and positively correlated with changes in preventative health behaviors and changes in self‐perceived physical health. Changes in preventative health behaviors partially mediated the relation between changes in conscientiousness and changes in self‐perceived physical health. Conclusions This longitudinal study extends previous research on conscientiousness and health by exploring the relations between latent variables over a 3‐year period. It provides evidence that increases in conscientiousness and preventative health‐related behaviors are associated with improvements in self‐perceived health over the same time period.