This study analyzes the longitudinal association between precarious employment and physical and mental health in a dualized labor market by disaggregating between-employee and within-employee effects and considering mobility in precariousness of employment. Analyses were based on the German Socio-Economic Panel from 2002 to 2018 considering all employees ages 18 to 67 years (n = 38,551). Precariousness of employment was measured as an additive index considering working poverty, nonstandard working time arrangements, perceived job insecurity, and low social rights. Health outcomes were mental and physical health. Random effects models were used and controlled for sociodemographic and socioeconomic variables. Results indicated that the association between precariousness of employment and mental and physical health is mainly based on between-employee differences and that prolonged precariousness of employment or upward or downward mobility are associated with poor health. We found evidence of polarization in health by precariousness of employment within a dualized labor market.