Introduction: Following a cardiac event it is recommended that cardiac patients participate in cardiac rehabilitation (CR) programs. However, little is known about the relative cost-effectiveness of lifestyle-related interventions for cardiac patients. This study aimed to compare the cost-effectiveness of a telephone-delivered Healthy Weight intervention to a telephone-delivered Physical Activity intervention for patients referred to CR in urban and rural Australia. Methods: A cost-utility analysis was conducted alongside a randomised controlled trial of the two interventions. Outcomes were measured as Quality Adjusted Life Years (QALYs) gained. Results: The estimated cost of delivering the interventions was $201.48 per Healthy Weight participant and $138.00 per Physical Activity participant. The average total cost (cost of health care utilisation plus patient costs) was $1,260 per Healthy Weight participant and $2,112 per Physical Activity participant, a difference of $852 in favour of the Healthy Weight intervention. Healthy Weight participants gained an average of 0.007 additional QALYs than did Physical Activity participants. Thus, overall the Healthy Weight intervention dominated the Physical Activity intervention (Healthy Weight intervention was less costly and more effective than the Physical Activity intervention). Subgroup analyses showed the Healthy Weight intervention also dominated the Physical Activity intervention for rural participants and for participants who did not attend CR. Conclusions: The low-contact pedometer-based telephone coaching Healthy Weight intervention is overall both less costly and more effective compared to the Physical Activity intervention, including for rural cardiac patients and patients that do not attend CR. Â© 2015 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ).