Mindfulness meditation is a well-validated intervention for symptoms of depression and anxiety disorders in adults, with meta-analyses showing moderate effect sizes. This study marks the first published meta-analysis of the burgeoning literature on mindfulness meditation with youth (conducted between 2004 and 2011) and identifies specific outcomes and sub-populations for whom mindfulness may be particularly helpful. Inclusion criteria were peer-reviewed journal articles published in English, study participants under 18 years of age, and a description in the methods section of mindfulness as the chief component of an intervention. A systematic search was conducted, of which upon review, 20 articles met inclusion criteria. Mindfulness interventions with youth overall were found to be helpful and not to carry iatrogenic harm, with the primary omnibus effect size (del) in the small to moderate range (0.23, p < .0001), indicating the superiority of mindfulness treatments over active control comparison conditions. A significantly larger effect size was found on psychological symptoms compared to other dependent variable types (0.37 vs. 0.21, p = .028), and for studies drawn from clinical samples compared to non-clinical sample (0.50 vs. 0.20, p = .024). Mindfulness appears to be a promising intervention modality for youth. Although to date the majority of studies on mindfulness with youth engage generally healthy participants recruited from schools, the findings of this meta-analysis suggest that future research might focus on youth in clinical settings and target symptoms of psychopathology.