ObjectiveAlthough seatbelt wearing rates among drivers and other vehicle occupants are relatively high in Australia, approximately-one third of vehicle occupants killed in crashes are unrestrained. The aim of this study was to identify factors that predict intentions to always wear a seatbelt as both a driver and passenger, through the use of an extended Theory of Planned Behaviour (TPB). MethodsThis study used a mixed methods design, consisting of both qualitative (Phase 1- focus groups) and quantitative (Phase 2- Survey) methods with licensed Queensland (state of Australia where the study was conducted) drivers. In Phase 2, a convenience sample of 125 participants responded to an online survey. The survey assessed intentions to always wear a seatbelt both as a driver and as a passenger. ResultsThe results of Phase 1 revealed the salient normative, behavioural, and control beliefs underpinning this behaviour. These beliefs were incorporated into the survey for Phase 2. The results of Phase 2 identified that the standard TPB constructs accounted for 70.5% of the variance in intention to always wear a seatbelt as a driver and 51% of the variance in intention as a passenger. However, perceived behavioural control (PBC) and subjective norm were the only significant predictors of intention to always wear a seatbelt as a driver, while subjective norm was the only significant predictor of intention as a passenger. The extended TPB explained a significant amount of additional variance over and above the standard TPB for both the driver (2.1%) and the passenger (15.2%) contexts. Mediation analyses also confirmed the importance of considering not only the direct but also indirect effects of the study’s key constructs. Results confirmed the perspective that past behaviour’s effect is at least partially, and in the case of the relationship between past behaviour and attitude, fully mediated by habit. ConclusionThe results confirmed that while most participants reported always wearing their seatbelt irrespective of whether they were said to be a driver or passenger in a vehicle, there are some instances where they may be less likely to wear their seatbelt. The study highlights the complexities associated with understanding the motivations of seatbelt wearing intentions and the need for further research to ensure the motivations underpinning seatbelt use are well-understood. Such motivations need to be clear to help inform the development of future, targeted interventions to enhance seatbelt wearing intentions and ultimately behaviour.