An emerging body of research demonstrates the effectiveness of Acceptance and Commitment Therapy (ACT) in the treatment of adult psychopathology, with several reviews and meta-analyses attesting to its effectiveness. While there are comparatively fewer empirical studies of child populations, the past few years has seen burgeoning research interest in the utility of ACT for problems in childhood. A systematic review of the published and unpublished literature was conducted to examine the evidence for ACT in the treatment of children and to provide support for clinical decision making in this area. Searches of PsycInfo, PsycArticles, PsycExtra, Proquest and the Association for Contextual Behavioral Science databases were undertaken, as well as reference lists and citation searches conducted, up to December 2014. Broad inclusion criteria were employed to maximise review breadth. Methodological quality was assessed and a narrative synthesis approach adopted. Twenty-one studies covering a spectrum of presenting problems met inclusion criteria, with a total of 707 participants. Studies were predominantly within-group designs, with a lesser proportion of case studies/series, between-group and randomised controlled trials. The preponderance of evidence suggests ACT results in improvements in clinician, parent and self-reported measures of symptoms, quality of life outcomes and/or psychological flexibility, with many studies demonstrating further gains at follow-up assessment. However, several methodological weaknesses limit conclusions, including small samples, non-randomised designs, and few alternative treatment or control comparisons. While larger scale, methodologically rigorous trials from a broader research teams are needed to consolidate these preliminary findings, emerging evidence suggests ACT is effective in the treatment of children across a multitude of presenting problems. ACT may be a viable alternative treatment option for clinicians working with young people.