Informal caregivers make a substantial contribution to cancer care. However, the impact of caregiving on caregivers’ own dietary behaviours remains poorly understood and nutrition support for this population is largely absent from current cancer care services (1). This research investigated how the caregiving role influenced dietary behaviours and developed and evaluated a nutrition-focused intervention designed specifically for cancer caregivers. The research was conducted across three interconnected phases informed by Integrated Knowledge Translation (IKT) principles. Phase 1 used qualitative methods to explore caregivers’ experiences of dietary change during cancer caregiving. Phase 2 engaged caregivers, health professionals and cancer-sector stakeholders in a co-production process to identify key intervention requirements and develop a tailored nutrition-focused health coaching intervention. Phase 3 employed an exploratory sequential mixed-methods feasibility study to evaluate the intervention’s acceptability and feasibility among Australian cancer caregivers. Data collection included qualitative interviews, advisory board consultations, validated dietary self-efficacy and food literacy measures, and post-intervention acceptability assessments. Findings demonstrated that becoming a cancer caregiver frequently resulted in significant dietary behaviour change, with outcomes varying from dietary improvement to deterioration. Changes were influenced not only by patient-related factors but also by caregivers’ own beliefs, responsibilities, competing priorities and psychosocial circumstances. Caregivers described a strong sense of responsibility for patient nutrition, often prioritising patient needs over their own health. Dietary changes occurred across all stages of the caregiving trajectory. Co-production identified six critical intervention requirements: flexibility, individualisation, practical content, non-clinical positioning, perceived value, and appropriate timing of engagement. These findings informed the development of a nutrition-focused health coaching intervention grounded in Motivational Interviewing (MI) and behaviour change theory. Thirty-one caregivers enrolled in the intervention and 26 completed all coaching sessions (83.9% retention). Participants reported high levels of acceptability and perceived benefit, with improvements observed in dietary self-efficacy and food literacy. Qualitative findings indicated that caregivers valued being recognised as individuals rather than solely as members of a patient-caregiver dyad and reported increased confidence, self-awareness and ability to prioritise their own nutrition. This study provides novel evidence that cancer caregiving influences dietary behaviours through complex behavioural and psychosocial mechanisms and demonstrates that a co-produced, nutrition-focused intervention is both feasible and acceptable. The findings support greater recognition of caregiver nutrition within cancer care and provide a foundation for future effectiveness trials and implementation research.