The aim of this thesis was to investigate the relationship between physical activity (PA) and depression in people with coronary heart disease (CHD). I conducted three studies to explore this topic. In Study 1, I examined the relationship between PA and depression, over time, in people with CHD. In Study 2, I explored the PA experiences of people with both depression and CHD, and in Study 3, I designed and implemented a PA adherence intervention, with the aim of increasing adherence to PA for people with depression and CHD. ... Overall, the findings of the present thesis highlight the prevalence and severity of depression after a cardiac event and the ongoing negative relationship between depression and PA, and depression and exercise SOC, in people with CHD. In addition, the intervention study showed promising results for an adherence intervention based on an exercise consultation approach, and these findings suggest that exercise adherence interventions have potential for reducing depression and increasing PA in people with CHD.