Objective: To analyze the effectiveness of psychological treatments on symptom load and associated disability in children with functional somatic symptoms, and to explore potential moderators of effects. Study design: Cochrane, PubMed, PsycINFO, EMBASE, and CINAHL were searched for randomized controlled trials published in peer-reviewed journals. Randomized controlled trials studying the effect of a psychological treatment on symptom load and disability in children with functional somatic symptoms were selected. Data on symptom load, disability, and school absence directly post-treatment and at follow-up were extracted by 2 assessors. Studies were appraised with the Cochrane risk of bias tool. Standardized mean differences were pooled in a random-effects model. Heterogeneity in effect-sizes was explored by use of meta-regressions. PROSPERO Registration ID: CRD42015029667. Results: Out of 4098 identified records, 27 studies were included in this review of which 21 were included in meta-analyses. Psychological treatments reduced symptom load (Hedges g = -0.61), disability (Hedges g = -0.42), and school absence (Hedges g = -0.51) post-treatment in children suffering from various functional somatic symptoms. Effects were maintained at follow-up. Type and duration of symptoms, age, and treatment dose did not explain heterogeneity in effect-sizes between studies. Effect-sizes should be interpreted with caution because of the variety in outcome measures, unexplained heterogeneity in found effects and potential publication bias. Conclusions: Psychological interventions reduce symptom load, disability, and school absence in children with functional somatic symptoms. Future research should clarify which patient and treatment characteristics modify outcomes.