93Background: Efforts to increase physical activity in cancer survivors have typically been facility-based, and results have generally not been durable. Home-based interventions provide a more feasible option, and are likely to produce longer-lasting benefits. Wearable trackers present a novel opportunity for monitoring physical activity in a practical way. The Health Action Process Approach model suggests that strategies such as action-planning and overcoming barriers may be effective for transitioning individuals from intention to behavioural change. This trial aims to increase physical activity in cancer survivors at cardiovascular risk, by implementing a 24-week self-monitoring and action-planning intervention using Fitbits. Methods: Sixty-eight cancer survivors were recruited to participate in the trial. Eligibility criteria included: insufficiently physically active, presence of cardiovascular risk factors, and completion of active cancer treatment in the five years prior to recruitment. Trial assessments are performed at baseline, 12-weeks, and 24-weeks, and measure physical activity (using 7-day accelerometer data), BMI, blood pressure, physical activity attitudes, barriers and perceived outcomes. Participants were randomly allocated to treatment and control groups, following the baseline assessment. Each participant in the treatment group was given a Fitbit Alta to monitor activity for the 24-week trial, attended two 2-hour group sessions involving goal-setting and action-planning activities, and a follow-up phone call to ensure program adherence. Results: Data collection is currently underway. Data analysis will use the Group x Time interaction from a General Linear Mixed Model analysis. Conclusions: As the population of cancer survivors is largely inactive and at cardiovascular risk, interventions are warranted. Specifically, physical activity interventions that are feasible, have robust theoretical underpinnings, and suit the preferences of cancer survivors post-treatment, show promise as a long-term solution. Clinical trial information: 2617000131358.