Type D personality is associated with unhealthy behaviour and poor subjective health in the general population. This study investigated whether health behaviour mediates the relationship between Type D and subjective health. There were 217 participants who completed measures of Type D, health-related behaviour, physical symptoms and quality of life. Type D individuals reported significantly less healthy behaviour and significantly poorer subjective health than non-Type Ds. In addition, it was found that health behaviour partially mediates these relationships. The study demonstrates that health behaviour may partly explain the relationship between Type D and poor health outcomes.