Background: Relationship quality and sleep quality influenced physiological and psychological health. Therefore, the aim of the present study was to determine a possible connection between relationship satisfaction and sleep quality and to test a theoretical model of sleep quality as related to relationship and psychological well-being. Methods: Fifty-one heterosexual, cohabitating couples between 24 and 70 years old participated. The relationship quality was measured by the German short version of relationship questionnaire. To determine the sleep quality, the Pittsburgh Sleep Quality Index and a two-week sleep diary were implemented. To gather information about psychological well-being, especially depression and anxiety, the German Symptom Checklist was used. Results: Sleep quality was measured by the Pittsburgh Sleep Quality Index and relationship quality correlated significantly negative. In addition, the study found a positive correlation between sleep duration and relationship quality. In a multiple regression model, fighting and mental strain explained 38% of variance of sleep quality. Depression, anxiety and relationship quality showed no further improvement of the model. These findings suggested that relationship quality, constructive partnership behavior and mental strain played an essential role in sleep quality.