Background/Aims: Childhood-onset hypertension is associated with cardiovascular morbidity and adult mortality. This study aimed to assess guideline-adherent hypertension among Taiwanese youth and the agreement on hypertension between the 2017 American Academy of Pediatrics guidelines and the 2004 Fourth Report. Methods: In this cross-sectional study, we collected outpatient blood pressure (OBP) measurements obtained during routine care visits from a large healthcare delivery system between 2009 and 2018 to evaluate the rate of guideline-adherent hypertension and assess patient-related factors of pediatric hypertension. Results: In total, 12,469 children and adolescents who underwent three separate ≥3 OBP measurements over 33,369 person-years with a total of 95,608 BP measurements in an outpatient setting were analyzed. According to the 2017 American Academy of Pediatrics (AAP) guidelines, the rate of pediatric hypertension in the study setting, which included participants aged 1 to 17 years, ranged from 0.78 to 5.95 per 1000 persons. Although there was perfect agreement between the thresholds of the two guidelines for defining hypertension in the age groups of 1–7, 8–12, and 13–17 years (all κ statistic ≥ 0.85), the use of the AAP threshold classified more adolescents as having hypertension. Children and adolescents with hypertension often had complex chronic diseases and required substantial healthcare services in outpatient, emergency, and inpatient settings. Conclusions: The present study provides evidence of guideline-adherent pediatric hypertension and highlights the importance of regularly monitoring blood pressure to identify and manage hypertension in children and adolescents. Further research is required to determine the impact of new thresholds on the detection of target organ damage at a pediatric age.