Prior research demonstrated influences of personality traits and their development on later status of subjective health and loneliness. In the present study, we intended to extend these findings by examining mutual influences between health‐related characteristics and personality traits and their development over time. German adults were assessed at two time points across 15 years (NT1 = 654, NT2 = 271; Mage at Time 1 = 24.39, SD = 3.69). Data were analyzed with multivariate structural equation models and a multivariate latent change model. Neuroticism was found to predict later levels and the development of subjective health and loneliness. While subjective health likewise predicted later levels of Neuroticism, loneliness was found to be predictive of later levels as well as the development of Neuroticism, Extraversion, and Conscientiousness. Correlated changes indicated that developing a socially more desirable personality is associated with slower declines in subjective health and slower increases in loneliness. The findings indicate that characteristics related to an individual's health are reciprocally associated with personality traits. Thus, the study adds to the understanding of the development of personality and health‐related characteristics.