Introduction: Young drivers continue to be overrepresented in road crash statistics and smartphone use has been identified as a dangerous form of driver distraction. Previous research has identified factors encouraging drivers to use their mobile phone, with few examining what deters drivers. This study examines the influence of legal and non-legal deterrents on smartphone use while driving (SWD) in a young adult sample. Method: An online survey was administered to a sample of 524 Australian drivers aged 17–25 years. Measures included demographic variables, legal deterrents (certainty, severity, and swiftness), and non-legal deterrents: social loss (peers and parents), internal loss (anticipated regret) and physical loss (injury to self/others). Self-reported SWD was the outcome variable, measured separately for initiating SWD and responding SWD behaviors. Results: Responding behaviors were reported more frequently than initiating, and social, internal, and physical loss were perceived as higher for initiating versus responding behaviors. Anticipated action regret and physical loss were significant negative predictors of SWD across both modalities of communication. Anticipated inaction regret was also a significant positive predictor of initiating behaviors. Both legal deterrents and social loss were non-significant predictors for both modalities of SWD. Conclusions: The results reinforce previous evidence showing that legal deterrence variables are not consistently effective at reducing offending behaviors. Future research should continue to explore the effect of non-legal deterrents across different modalities of SWD. Practical implications: Road safety interventions aimed at young drivers should evaluate the impact of highlighting anticipated regret and potential injury to self and others associated with risky driving behaviors, such as SWD.