The popularity of mindfulness-based interventions (MBIs) is growing rapidly in schools. Decisions regarding the use of these interventions must be based on empirical evidence. There is robust evidence for the use of MBIs with adults, but research on MBIs with youth is nascent. The purpose of this meta-analytic review was to add to the literature by synthesizing single-case research on MBIs with children and adolescents. Specifically, the effect of MBIs on youths’ disruptive behavior was examined in 10 studies published between 2006 and 2014. Results indicated that, on average, MBIs had a medium effect on disruptive behavior during treatment, g = 1.04, 95% confidence interval (CI) [0.30–1.78]; TauU = 0.59, 95% CI [0.40–0.77]. The average effect of MBIs during maintenance phases was larger, g = 1.41, 95% CI [0.55–2.28]; TauU = 0.71, 95% CI [0.59–0.83]. Potential moderators of intervention effects were also explored. Implications for future research and practice regarding MBIs with youth and in schools are discussed.