BACKGROUND: Guidelines recommend neck exercise as a key intervention for chronic non-specific neck pain, yet current exercise programmes show modest effects and poor patient engagement. This study aimed to co-develop a neck exercise programme that maximizes effectiveness and engagement. METHODS: Intervention Mapping steps 1-4 were employed with input from a diverse patient group (n = 17). In Step 1, outcomes/changes that the intervention aims to improve were synthesized from literature and patient workshops. To maximise engagement, Step 2 identified target behaviours (performance objectives), and their determinants from clinical guidelines, literature, and patient workshops. In Step 3, change techniques for each determinant were selected using the Theory and Techniques Tool and patient workshops. Techniques were organized into a logic model and framed within a "best fit" existing behaviour change theory to guide clinical practice. To maximise effectiveness, Step 2 identified exercise objectives from systematic reviews and expert consensus, describing the mechanisms through which exercise affects outcomes. Step 3 identified the most effective exercises and tailoring strategies to optimise exercise objectives. Resources to support delivery in clinical practice were co-developed with patients and physiotherapists in Step 4. RESULTS: The EPIC-Neck intervention aims to improve outcomes including pain, disability, function, sleep, mental well-being and relationship impact, based on individual patient needs. A biopsychosocial exercise prescription framework informs exercise tailoring to optimize neuromuscular function, pain self-efficacy, night pain, cognitive control, social support; and reduce catastrophic thinking/fear avoidance, depending on a patients desired outcome. Patients need to achieve four performance objectives to manage neck pain effectively with exercise: (1) performing specific neck exercises, (2) independently adapting and progressing their neck exercises, (3) using specific neck exercises during flare-ups, and (4) initiating general exercise. To maximise engagement, a facilitation guide was developed based on the Process Model of Lifestyle Behaviour Change. The guide addresses 35 determinants using 24 change techniques, including goal setting, motivation enhancement, social support, action planning, self-monitoring, problem-solving support, shared decision-making, and patient-centred communication. CONCLUSION: This study co-developed an evidence-informed, theoretically driven exercise programme designed to enhance both effectiveness and patient engagement. Future work will assess its feasibility and acceptability to patients and physiotherapists, and in the long-term establish its clinical and cost-effectiveness.