OBJECTIVES: To assess the feasibility of delivering and evaluating a lifestyle programme for patients with colorectal cancer undergoing potentially curative treatments. STUDY DESIGN: Non-randomised feasibility trial. SETTING: National Health Service (NHS) Tayside. PARTICIPANTS: Adults with stage I-III colorectal cancer. INTERVENTION: The programme targeted smoking, alcohol, physical activity, diet and weight management. It was delivered in three face-to-face counselling sessions (plus nine phone calls) by lifestyle coaches over three phases (1: presurgery, 2: surgical recovery and 3: post-treatment recovery). PRIMARY OUTCOME: Feasibility measures (recruitment, retention, programme implementation, achieved measures, fidelity, factors affecting protocol adherence and acceptability). SECONDARY OUTCOMES: Measured changes in body weight, waist circumference, walking and self-reported physical activity, diet, smoking, alcohol intake, fatigue, bowel function and quality of life. RESULTS: Of 84 patients diagnosed, 22 (26%) were recruited and 15 (18%) completed the study. Median time for intervention delivery was 5.5 hours. Coaches reported covering most (>70%) of the intervention components but had difficulties during phase 2. Evaluation measures (except walk test) were achieved by all participants at baseline, and most (<90%) at end of phase 2 and phase 3, but <20% at end of phase 1. Protocol challenges included limited time between diagnosis and surgery and the presence of comorbidities. The intervention was rated highly by participants but limited support from NHS staff was noted. The majority of participants (77%) had a body mass index>25 kg/m CONCLUSIONS: To make this intervention feasible for testing as a full trial, further research is required on (a) recruitment optimisation, (b) appropriate assessment tools, (c) protocols for phase 2 and 3, which can build in flexibility and (d) ways for NHS staff to facilitate the programme. TRIAL REGISTRATION NUMBER: ISRCTN52345929; Post-results.