This study attempts to identify the persuasive design principles of car-related smartphone apps that assist users in driving or managing their vehicles. We developed a guideline by experts for evaluating persuasive design principles of car apps and recruited four evaluators who were trained to apply the guideline and given 35 car apps for evaluation. The value of Fleiss’ Kappa was 0.782, over the excellent criterion of 0.75, which means the inter-rater reliability of persuasive design guideline was reliable. We collected 697 car apps from Apple iTunes Store and Google Play and examined which design principles were implemented by these car apps. The result shows that nine persuasive design principles are found, such as reduction, trustworthiness, real-world feel, self-monitoring, personalization, reminder, suggestion, expertise, and verifiability. The results from this study would suggest some implications for car app developers and automakers to develop better car apps in the future.