Background: The error-related negativity (ERN) and the error positivity (Pe) are electrophysiological signals linked to error processing, a crucial aspect of self-monitoring and regulation. Previous research suggests different developmental trajectories for the ERN and Pe, with the ERN increasing in strength during the course of childhood and adolescence, while the Pe appears to reach a plateau by late childhood. There are, however, reports that are discrepant with this pattern, and effects of participant, task and methodological characteristics are poorly understood. The main objectives of this systematic review and meta-analysis are to evaluate the effect of age on ERN and Pe magnitude in children and adolescents, and to examine potential moderators of these effects, including age, sex, experimental task, task difficulty, and topography and quantification of the ERN and Pe. Methods/design: Studies that report group differences between age-groups or associations with age for the ERN and/or Pe magnitude in typically developing children and/or adolescents will be identified. The literature search will be conducted through PubMed and Scopus, all abstracts will be screened, and reference lists of relevant articles cross-checked for inclusion. The present protocol will also be disseminated on social media platforms to call for unpublished data. The data will be extracted from the eligible studies and will be included in random-effect meta-analyses in R. The results will include the estimation of age and age-group effect sizes, heterogeneity, risk of publication bias, and effects of moderating variables. Discussion: The study will include a systematic literature search and meta-analyses to better understand age-related differences in the ERN and Pe magnitudes. The results will provide estimates of effect sizes that are relevant for calculating statistical power and sample sizes for future studies. In addition, it will provide benchmark effect sizes for typical development of the ERN and the Pe that could be used for comparison purposes in developmental studies of clinical or at-risk groups.