Background Physical activity is positively associated with survival and quality of life among breast cancer survivors. Despite these benefits, the majority of breast cancer survivors are insufficiently active. The potential health benefits of reducing sedentary behaviour (sitting time) in this population have not been extensively investigated. The ACTIVATE Trial will evaluate the efficacy of an intervention that combines wearable technology (the Garmin Vivofit2®) with traditional behavioural change approaches to increase physical activity and reduce sedentary behaviour performed by breast cancer survivors. Methods/design This randomised controlled trial includes inactive, postmenopausal women diagnosed with stage I-III breast cancer who have completed their primary treatment. Participants are randomly assigned to the primary intervention group (Garmin Vivofit2® behavioural feedback and goal setting session; and, five telephone-delivered health coaching sessions) or to the wait-list control group. The primary intervention is delivered over a 12-week period. The second 12-week period comprises a maintenance phase for the primary intervention group, and an abridged intervention (Garmin Vivofit2® only) for the wait-list control group. Moderate- to vigorous-intensity physical activity (MVPA) and sedentary behaviour are assessed by accelerometry at baseline (T1), end of intervention (T2), and end of maintenance phase (T3). Discussion The ACTIVATE Trial is one of the first studies to incorporate wearable technology into an intervention for cancer survivors. If the use of wearable technology (in combination with behaviour change strategies, or alone) proves efficacious, it may become an inexpensive and sustainable addition to the health promotion strategies available to health care providers in the cancer survivorship context. Trial registration: ACTRN12616000175471.