BACKGROUND: 'Caring for Country' is defined as Indigenous participation in interrelated activities with the objective of promoting ecological and human health. Ecological services on Indigenous-owned lands are belatedly attracting some institutional investment. However, the health outcomes associated with Indigenous participation in 'caring for country' activities have never been investigated. The aims of this study were to pilot and validate a questionnaire measuring caring for country as an Indigenous health determinant and to relate it to an external reference, obesity. METHODS: Purposively sampled participants were 301 Indigenous adults aged 15 to 54 years, recruited during a cross-sectional program of preventive health checks in a remote Australian community. Questionnaire validation was undertaken with psychometric tests of internal consistency, reliability, exploratory factor analysis and confirmatory one-factor congeneric modelling. Accurate item weightings were derived from the model and used to create a single weighted composite score for caring for country. Multiple linear regression modelling was used to test associations between the caring for country score and body mass index adjusting for socio-demographic factors and health behaviours. RESULTS: The questionnaire demonstrated adequate internal consistency, test-retest validity and proxyrespondent validity. Exploratory factor analysis of the 'caring for country' items produced a single factor solution that was confirmed via one-factor congeneric modelling. A significant and substantial association between greater participation in caring for country activities and lower body mass index was demonstrated. Adjusting for socio-demographic factors and health behaviours, an inter-quartile range rise in caring for country scores was associated with 6.1 Kg and 5.3 Kg less body weight for non-pregnant women and men respectively. CONCLUSION: This study indicates preliminary support for the validity of the caring for country concept and a questionnaire designed to measure it. This study also highlights the importance of investigating Indigenous-asserted health promotion activities. Further studies in similar populations are merited to test the generalisability of this questionnaire and to explore associations with other important Indigenous health outcomes.