This study compared brief instruction in mindfulness versus somatic relaxation in their ability to reduce rumination and negative affect following an induced negative mood and ruminative self-focus. A nonclinical undergraduate sample (N = 114; 61% women) participated. Based on previous research using intensive mindfulness training, we predicted that brief instruction in mindfulness would be unique in its ability to reduce rumination relative to somatic relaxation and no-treatment control groups. Findings partially supported our hypothesis. For women, mindfulness was better at reducing rumination compared to no treatment, while for men somatic relaxation was better than mindfulness and no treatment. Furthermore, we found support for a moderated mediation model where reductions in rumination accounted for decreased negative affect only for women. Future research should examine whether these preliminary findings can be replicated and expanded, because they may have important implications regarding treatment matching based on gender. Utility of brief interventions for emotion regulation is also discussed.