According to the systemic-transactional stress model (STM; G. Bodenmann, European Review of Applied Psychology, 1997; 47: 137), extradyadic stress from daily hassles can have a negative impact on the individual psychological and physical health and the couple's relationship. This study is the first one to test the STM propositions in a model that includes both partners' individual and relational outcomes simultaneously. The model also includes actor and partner effects as well as the interdependence between partners' processes. Cross-sectional, self-report data were collected from 110 community couples in Switzerland. Consistent with STM predictions, results from the path model analysis indicate that for actor effects extradyadic stress from daily hassles relates directly to lower psychological (increase in anxiety symptoms) and physical well-being and only indirectly to lower relationship satisfaction through increased intradyadic stress from relationship problems and also through more depressive symptomatology in men. The female extradyadic stress and intradyadic stress had partner effects on the male intradyadic stress and the male relationship satisfaction, respectively. Limitations as well as research and clinical implications for marriage and family therapists are discussed.