With the progressive elimination of mercury column devices for blood pressure (BP) measurement in children and adolescents, valid alternatives are needed. Oscillometric devices provide a replacement without mercury, are fully automated, and have excellent reliability among evaluators. Here, the goal was to test the accuracy of automatic blood pressure monitor devices compared to the mercury sphygmomanometer for BP measurement in children and adolescents. Electronic databases are EMBASE, MEDLINE (PubMed), SCOPUS, and Web of Science. We selected 8974 potentially eligible articles and two authors independently. We separately reviewed 370 full papers. Potentially eligible articles were selected according to the following criteria: (a) articles published in Portuguese, English, and Spanish; (b) screening of titles; (c) screening of abstracts; and (d) retrieval and screening of the full article to determine whether it met the inclusion criteria. We included 45 articles for analysis, 28 of which were selected for meta-analysis. The systolic BP measured by automatic blood pressure monitors presents 1.17 mmHg on average (95% CI 0.85; 1.48); for diastolic BP, it produced -0.08 mmHg (95% CI -0.69; 0.54) compared with a mercury sphygmomanometer. There is high heterogeneity between studies (> 90%) in the meta-analysis, partly explained by the device model, study environment, and observer training. Only articles that reported BP measurement by both methods were included.Conclusion: Automatic blood pressure monitors have strong measurement validity when compared with the mercury column. Thus, these can be safely used in blood pressure measurements of children and adolescents in clinical and epidemiological studies. What is Known: •The "gold standard" for indirect BP measurement is the mercury sphygmomanometer. •The accuracy of the automatic device is critical to any blood pressure measurement method. What is New: •Oscillometric or automatic devices can be a suitable alternative to auscultation for initial screening, consistent with current pediatric guidelines. •The automatic devices compared to the mercury column have a good validity of measurements, which can be used in blood pressure measurements of children and adolescents in clinical and epidemiological settings, provided that international protocols are followed.