The oil and gas industry is a vital contributor to the global economy and a key source of employment within oil-producing countries. Oil production is largely dependent on a skilled population who are adept in coping with the demands of an offshore environment. Due to the high risk nature of work offshore, it is a requisite that personnel engage in health promoting behaviours. The research aimed to identify aspects of offshore workers self care which required behaviour change and the behavioural determinants which were associated with engagement in self care. A mixed methods design was utilised to generate novel data and original findings. Phase 1 used a quantitative cross-sectional online survey to assess offshore workers’ (n=352, 53.6% response rate) health, quality of life, mental wellbeing and self care status. The findings highlighted key areas of concern, as indicated by negative scoring across measures, relating to: overweight/obesity; medication adherence; absenteeism (with regard to travelling offshore); medical evacuation; lack of adherence to 5-a-day fruit and vegetable guidelines; physical activity; smoking; hazardous alcohol use, and insomnia. Phase 2 used qualitative theory-based telephone interviews to explore self care behaviours from the perspective of offshore workers (n=16). Offshore workers who had completed a survey and indicated they would like to receive further information on the interviews were invited to participate. Both the interview schedule and data analysis were informed by the Theoretical Domains Framework (TDF). Healthy eating and physical activity were the behaviours most frequently discussed by offshore workers and identified as areas requiring behaviour change. TDF domains representing both behaviours included: beliefs about capabilities; beliefs about consequences; intentions; goals; memory, attention and decision processes; environmental context and resources; social influences; emotion, and behavioural regulation. Phase 3 used qualitative theory-based telephone interviews to explore offshore workers’ (n=13) self care behaviours from the perspective of remote healthcare practitioners. Both the interview schedule and data analysis were informed by TDF. Healthy eating and harmful/hazardous alcohol use were the behaviours most frequently discussed by remote healthcare practitioners and identified as areas requiring behaviour change. TDF domains representing both behaviours included: knowledge; environmental context and resources; social influences; emotion, and behavioural regulation. The findings, when triangulated suggest that offshore workers may benefit from the implementation of a self care intervention which targets healthy eating, physical activity and alcohol consumption. It is advised that the intervention target multiple self care behaviours and that development is underpinned by behaviour change theory to ensure effectiveness. The intervention may be tailored in accordance with the TDF domains identified in this research as determinants of healthy eating, physical activity and alcohol use behaviours.