Background: The implications of cancer and its medical treatment are traumatic, highly stressful and have great psychosocial impact. Therefore, a comprehensive treatment is essential and music-based interventions can play an important role. The objective of this study is to summarise research that assesses the effects of music therapy in paediatric and adolescent patients with cancer during the process of the disease. Methods: A systematic review conducted following PRISMA’s statements. An electronic search of the literature was carried out in the following databases: PubMed, Cochrane, Dialnet, Scopus, IDICEs CSIC and Science Direct. Original studies that conducted music-based interventions with oncology patients between 0 to 18 years old were included. Results: 11 studies were finally included in the review. The sample consisted of two quasi-experimental studies, five randomised clinical controlled trials, one non-randomised controlled trial, one study that involved qualitative and quantitative analysis methods, one descriptive study and one observational study. Conclusions: Music-based interventions decrease anxiety, perceived pain and depression symptoms and improve state of mind, self-esteem and quality of life of paediatric and adolescent patients with cancer. Moreover, they decrease heart rate, respiratory rate and blood pressure and encourage patients to use adaptive coping strategies.