Due to the amount of literature supporting exercise participation after cancer diagnosis, there has been recent interest in barriers to exercise engagement among cancer patients. However, little is known regarding reasons why people choose to disengage and how this disengagement occurs over time. This study aimed to qualitatively study the perceived barriers to exercise implementation, 5-year post-breast cancer diagnosis. Eighty-three female breast cancer survivors participated in a one-to-one semi-structured interview, regarding their experience of exercise over the past 5 years following their original participation in a group-based structured exercise intervention after diagnosis (41 from intervention and 42 from original control group). The data were analysed using inductive thematic analysis. The findings included three main themes and several subthemes regarding the women's perceived barriers: psychological barriers (lack of motivation, fears, dislike of gym, not being the 'sporty type'), physical barriers (the ageing process, cancer treatment and other physical co-morbidities, fatigue and weight gain) and contextual and environmental barriers (employment, traditional female care-giving roles, proximity/access to facilities, seasonal weather). The findings add inductive support to the current survivor health research advocating the use of activity immediately after diagnosis, as well as the need for tailored activity programmes in order to overcome potential obstacles.