Mindfulness is a state of being fully attentive to the current moment and is an experiential way of living in daily life. As a personal trait, mindfulness has been proven to enhance various negative emotions and behaviors. However, in the field of driving, there is still a lack of research on the mechanisms of mindfulness on anger expression behavior, specifically aggressive driving. Therefore, the purpose of this study is to reveal the impact of mindfulness on drivers’ aggressive driving behaviors and the mediating effect of driving anger and anger rumination. A total of 350 (208 males and 142 females) participants in China voluntarily completed a series of questionnaires, including the Mindful Attention and Awareness Scale (MAAS), the Driving Anger Scale (DAS), the Anger Rumination Scale (ARS) and the Driving Anger Expression Inventory (DAX). The hierarchical multiple regression analysis and pathway analysis results showed that mindfulness negatively predicted driving anger, anger rumination and driving anger expression. Moreover, driving anger and anger rumination mediated the relationship between mindfulness and driving anger expression, accounting for 9.51% and 18.74% of the total effect, respectively. The chain-mediated effect of driving anger and anger rumination accounted for 8.00% of the total effect. This study has revealed some of the internal mechanisms through which mindfulness reduces aggressive driving. It fills a part of the gap in understanding the protective role of mindfulness in the driving domain. Furthermore, it suggests mindfulness interventions for drivers, which may have the potential to enhance overall road safety.