Sleep duration has been associated with several health outcomes in children and adolescents. As an extensive number of questionnaires are currently used to investigate sleep schedule or sleep time, we performed a systematic review of criterion validation of sleep time questionnaires for children and adolescents, considering accelerometers as the reference method. We found a strong correlation between questionnaires and accelerometers for weeknights and a moderate correlation for weekend nights. When considering only studies performing a reliability assessment of the used questionnaires, a significant increase in the correlations for both weeknights and weekend nights was observed. In conclusion, moderate to strong criterion validity of sleep time questionnaires was observed; however, the reliability assessment of the questionnaires showed strong validation performance.