BACKGROUND: Although there are previous systematic reviews about the oral health-related quality of life (OHRQoL) impact among children and adolescents after orthodontics treatment, there is no definition for the magnitude of these impacts during the therapy. OBJECTIVE: To systematically analyse the literature on changes in the quality of life of children and adolescents during orthodontic treatment. LIMITATIONS: Almost all the studies included in this review are non-randomized clinical trials, which are susceptible to several biases that affect the certainty of evidence obtained, especially by confounding factors and the lack of a control group. CONCLUSIONS AND IMPLICATIONS: Based on very low certainty of evidence, wearing appliances does not seem to have a significant negative impact during the first year of orthodontic treatment. However, the meta-analytic results suggest that functional limitations in the first 3 months of treatment can be slightly more critical for the impact on the oral health quality of life and consequent patient adherence to treatment. FUNDING: This study was financed by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES), Conselho Nacional de Desenvolvimento Científico e Tecnológico - Brazil (CNPq), and Fundação de Amparo à Pesquisa do Estado de Minas Gerais - Brazil (FAPEMIG). REGISTRATION: CRD42021234407.