Children need to be equipped with the skills to respond effectively to stress and prevent poor decision-making surrounding alcohol and tobacco use. Training and practice in mindfulness is one possible avenue for building children's skills. Recent research has revealed that mindfulness education in the classroom may play a role in enhancing children's self-regulatory abilities. Thus, the goal of the current study was to extend existing research in mindfulness education in classrooms and conduct an assessment of the feasibility and effectiveness of a new mindfulness education, substance abuse prevention program for fourth- and fifth-grade children ("Master Mind"). Two elementary schools were randomly assigned to be an intervention group (n = 71) or wait-list control group (n = 40). Students in the intervention group were taught the four-week "Master Mind" program by their regular classroom teachers. At pre- and postintervention time points, students completed self-reports of their intentions to use substances and an executive functioning performance task. Teachers rated students on their behavior in the classroom. Findings revealed that students who participated in the "Master Mind" program, as compared to those in the wait-list control condition, showed significant improvements in executive functioning skills (girls and boys), as well as a marginally significant increase in self-control abilities (boys only). In addition, significant reductions were found in aggression and social problems (girls and boys), as well as anxiety (girls only). No significant differences across groups were found for intentions to use alcohol or tobacco. Teachers implemented the program with fidelity; both teachers and students positively rated the structure and content of the "Master Mind" program, providing evidence of program satisfaction and feasibility. Although generalization may be limited by the small sample size, the findings suggest that mindfulness education may be beneficial in increasing self-regulatory abilities, which is important for substance abuse prevention.