There are many health benefits with regular physical activity. Despite this, physical inactivity is a global health problem. It is therefore important to find ways of helping people become more physically active and maintain this behaviour over time. Imagery could be used to increase exercise adherence, but more research is necessary for it to be used in the best way. The aim of this thesis was to examine tenets of the revised applied model of deliberate imagery use in the exercise domain. Two studies were carried out to investigate whether: (1) a brief period of imagery rehearsal could increase barrier self-efficacy in women who want to exercise more; and (2) if it is feasible to improve imagery ability among women who want to exercise more through imagery training and one week of guided rehearsal. The studies were the first to improve barrier self-efficacy, affective responses, and imagery ability using a brief imagery intervention