In contrast to the percentile-based definitions of elevated blood pressure (BP) and hypertension for children and adolescents of all ages in the 2004 fourth report, the 2017 American Academy of Pediatrics (AAP) BP guideline recommends a change to single BP cut-offs for clinical diagnosis (120/< 80-129/< 80 mmHg for elevated BP and ≥ 130/80 mmHg for hypertension) in adolescents aged 13 years and older, and it also recommends researchers using the percentile-based definitions for more precise BP classification. The aim of our study was to assess the diagnostic effect of the single BP cut-offs for identifying adolescent abnormal BP as compared to the 2017 AAP percentile table by sex, age, and height. Data were from 8287 adolescents aged 13-17 years in NHANES 1999-2016 and 1659 adolescents aged 13-17 years in NHANES III (1988-1994). Compared to the 2017 AAP percentile table, the single BP thresholds performed well for identifying elevated BP in adolescents in NHANES 1999-2016/NHANES III, with high values of area under the curve 0.93/0.95, sensitivity 86.7%/89.9%, specificity 100%/100%, positive predictive value (PPV) 100%/100%, negative predictive value (NPV) 98.2%/98.8%, and kappa coefficient 0.92/0.94. The results were similar for identifying hypertension in the two datasets, with especially high PPV 100%/100% and NPV 99.2%/99.2%. However, the sensitivity values of the simple method for identifying hypertension were not satisfactory among girls, younger adolescents, and Hispanic adolescents in both datasets. In conclusion, the single BP cut-offs in general performed similarly well for identifying abnormal BP as compared to 2017 AAP percentile table, but not well in some subgroups.