Previous research has demonstrated that mindfulness-based stress reduction (MBSR) improves psychological functioning in multiple domains. However, to date, no studies have examined the effects of MBSR on moral reasoning and decision making. This single group design study examined the effect of MBSR on moral reasoning and ethical decision making, mindfulness, emotion, and well-being. Additionally, we investigated whether there was an association between the amount of meditation practice during MBSR and changes in moral reasoning and ethical decision making, emotions, mindfulness, and well-being. Results indicated that MBSR was associated with improvements in mindful attention, emotion and well-being. Further, amount of meditation practice was associated with greater improvement in mindful attention. Two-month follow-up results showed that, MBSR resulted in improvements in moral reasoning and ethical decision making, mindful attention, emotion, and well-being. This study provides preliminary evidence that MBSR may potentially facilitate moral reasoning and decision making in adults.