Negative mood has been linked to poorer sustained attention and increased mind wandering. Mindfulness training appears to reduce negative mood and mind wandering. The current study examined whether a mindfulness induction moderated the impact of a negative mood manipulation on sustained attention task performance and emotionally valenced mind wandering. One hundred and two participants underwent a mindfulness induction, relaxation induction, or were assigned to a wait-list control condition. Participants subsequently completed a negative mood manipulation and sustained attention task. Rates of negatively valenced mind wandering were lower in mindfulness induction participants relative to the control condition participants. Negatively valenced mind wandering was associated with poorer SART performance and greater reaction time variability following the thought probe in the control and relaxation conditions, but not the mindfulness condition. We suggest that brief mindfulness inductions may reduce the deleterious influence of negative mind wandering on sustained attention task performance.