Protection motivation theory is a pre-eminent health behaviour theory purposed to predict participation in health protection and risk behaviours. It has been widely applied across multiple behaviours, populations and contexts. In this conceptual review, we summarise research applying the theory and identify shortcomings and evidence gaps that limit reported inferences and impede theory and intervention development. Accordingly, we provide recommendations for best practices and suggestions for future research to resolve these limitations. Limitations identified include a dearth of comprehensive theory tests, sparse evidence of theory sufficiency, a lack of studies including additional constructs, overuse of correlational and cross-sectional research designs, a paucity of intervention studies and tests of theory-consistent mechanisms of action, few tests intrapersonal and environmental moderators of theory effects and measurement concerns. We provide recommendations to address these limitations including conducting comprehensive theory tests in support of nomological validity; incorporating past behaviour and other constructs to establish theory sufficiency and extend its scope; adopting cross-lagged panel and factorial experimental research designs to test directional effects, permit better causal inference and test mechanisms of action; testing effects of moderators to identify conditions that may affect theory applicability and developing measurement standards for study constructs and adopting non-self-report behaviour measures.