To determine the effectiveness of a pedometer-based telephone intervention on the physical activity levels of cardiac patients who did not attend a CRP.A randomised controlled trial was conducted with 215 patients referred to a CRP but who could not or chose not to attend. The 6-week intervention included self-monitoring of physical activity using a pedometer and step calendar; and behavioural counselling and goal setting sessions. Data were collected at baseline, 6 weeks and 6 months.Study groups did not differ significantly at baseline. After 6 weeks, improvements in total physical activity time (p=0.027), total physical activity sessions (p=0.003), walking time (p=0.013) and walking sessions (p=0.002) in the intervention group were significantly greater than the control group after adjusting for baseline differences, and remained significant at 6 months.The findings that the pedometer-based telephone intervention was successful in increasing physical activity levels in cardiac patients who did not attend a CRP could result in major health benefits for this group of people.The pedometer-based telephone intervention could be offered as an effective and accessible option for patients not attending a CRP to increase and maintain their physical activity levels after hospitalisation.