Objective: This article describes results from a randomized clinical trial of a mindfulness-based intervention for parents and children, Mindful Family Stress Reduction, on a behavioral measure of attention in youths, the Attention Network Task (ANT). Method: Forty-one parent–child dyads were randomly assigned to either the mindfulness-based intervention condition or a wait-list control. School-age youths completed the ANT before and after the intervention. Results: Results demonstrate significant, medium-size (f ² = –.16) intervention effects to the conflict monitoring subsystem of the ANT such that those in the intervention condition decreased in conflict monitoring more than those in the wait-list control. Youths in the intervention condition also showed improvements in their orienting subsystem scores, compared with controls. Conclusion: Mindfulness-based interventions for youths have potential utility to improve attentional self-regulation, and future research should consider incorporating measures of attention into interventions that use mindfulness training.