Chronic disease prevention programs that target physical inactivity and sedentary behaviour are often evaluated using self-report assessment tools. However, these tools may require additional validation to ensure relevance and efficacy for Indigenous peoples. The scope to which this occurs is yet to be systematically assessed within the literature. This review aimed to explore and define the range of self-report physical activity and sedentary behaviour assessment tools validated for Indigenous adults globally. Searches were conducted across seven electronic databases; resultant articles were screened against the inclusion and exclusion criteria by two reviewers. Analysis of the 15 included articles suggests that self-report physical activity and sedentary behaviour assessment tools have achieved varying levels of validity amongst Indigenous populations globally. Most studies rated as low cultural appropriateness on a 14-item Indigenous research quality appraisal tool, however, there was a significant moderate upward trend over time (P = 0.0328). Digital physical activity or sedentary behaviour assessment tools have not yet been validated within Indigenous adult populations and constitute an apparent gap in the literature. Established validation methods for other populations were commonly found to be inappropriate for Indigenous population groups. There were no evident trends regarding validation study methodology identified, signifying a more bespoke approach within Indigenous population groups. Therefore, meaningful consultation and project co-design may help to prevent the potential methodological redundancy when developing and validating physical activity assessment methods within Indigenous populations globally.