Mindfulness-Based Stress Reduction (MBSR) courses typically consist of 20 hours of training but smaller doses have been shown to be effective at reducing stress (e.g., Boettcher, et al., 2014). To isolate mindful focus from non-directed silent time, undergraduates were assigned to mindfulness meditation (MM) or control (C) conditions. Twice a week in class, MM listened to a 3-minute-long pre-recorded mindfulness body scan meditation, while C sat silently to control for the directed focus involved in meditating. With mobile applications, students measured their heart rates as an indicator of stress after meditation practice and before exams. We measured trait mindfulness and trait anxiety at pretest and then again at the end of 5 and 10 weeks. Participants also reported their valence and arousal before and after each 3-minute meditation or silence. We found that group assignment (e.g., MM or C) predicted final grades, and time spent meditating or sitting in silence voluntarily outside of class was negatively correlated with heart rate, anxiety, and impulsiveness. Voluntary meditation or silence practice outside of class was also positively correlated with trait mindfulness and negatively correlated with impatience. Together, these data provide support for subtle long-term effects of short meditation practice in class.