Rationale: There is a growing body of evidence that supports the use of physical activity during and after cancer treatment, although activity levels for patients remain low. As more cancer patients are treated successfully and treatment costs continue to escalate, physical activity may be a promising adjunct to a person-centered healthcare approach to recovery.Aim: The aim was to further understand how physical activity may enhance the recovery process for a group of mixed-site cancer patients.Objectives: The research investigated longitudinal changes in physical activity and perceived quality of life between 2 and 6 month’s post-exercise interventions. It also investigated support systems that enabled patients to sustain these perceived changes.Method: The respondent cohort comprised 14 mixed-site cancer patients aged 43-70 (11 women, 3 men), who participated in a 2-phase physical activity intervention that took place at a university in the South West of England, UK. Phase 1 consisted of an 8 week structured physical activity programme; Phase 2 consisted of 4 months of non-supervised physical activity. Semi-structured interviews took place 3 times over 6 months with each participant. Grounded theory informed the data collection and analysis which, in turn, facilitated theoretical development.Findings: Our findings propose 3 theories on the impact of physical activity for recovering cancer patients: (1) Knowledge gained through a structured exercise programme can enable recovering cancer patients to independently sustain physical activity to 4 month follow-up. (2) Sustaining physical activity for 6 months promotes positive changes in the quality of life indicators of chronic fatigue, self-efficacy, ability to self-manage and energy levels & (3) Peer support from patients facilitates adherence to a structured exercise programme and support from a spouse or life partner facilitates independently sustained physical activity to 4 month follow-up.Conclusions: This study demonstrates that qualitative research can provide an evidence base that could be used to support future care plans for cancer patients. Our findings also demonstrate that a physical activity intervention can be effective at helping cancer patients recover from the side effects of their treatment and we recommend that physical activity should become an adjunct therapy alongside traditional cancer treatments.