Exercise is beneficial for both physical and psychological wellbeing. Mobile software applications are a promising mode for initiation and maintenance of exercise but are under-studied. This study examined the effectiveness of the Couch to 5k exercise app for initiating exercise for 17 participants with a mixed method design. Participants were examined using the app over a three month period. Scales from the Health Action Process Approach were utilised to explore relationships among constructs such as self-efficacy, planning and action control in relation to exercise initiation and behaviour. The DASS and SF-8 were used to examine mood and well-being, respectively. Amount of exercise completed over time was also recorded. Overall, exercise increased within the sample. However, the researcher regarded the app as a starting point, as only one participant used the app for the entire usage period. For most participants, using the app prompted them to do exercise without the app and discover other options for exercise. To improve the Couch to 5k app it was recommended that the guide to achieve running 5 kilometres extend to a period of 10-12 weeks instead of 8, consider combining the Couch to 5k app with the adjunct Couch to 10k app and use techniques to aid self-regulation and monitoring that smartphones are capable of such as accelerometry, GPS tracking and alerts and reminders.