We aimed to evaluate the consequences of the 2017 pediatric hypertension definitions, compared with the 2004 pediatric hypertension definitions on the prevalence of hypertension and to assess the performance of these 2 sets of guidelines in predicting adult hypertension, metabolic syndrome, and left ventricular hypertrophy (LVH). This longitudinal study consisted of 3940 children (47% male; ages 3-18 years) who came from the Bogalusa Heart Study with 36-year follow-up since childhood. Hypertension was identified in 7% and 11% as defined in the 2004 and 2017 guidelines, respectively. The 2004 and 2017 guidelines demonstrated similar associations with adulthood hypertension, metabolic syndrome, and LVH. However, the proportion of children identified as having hypertension who developed adult LVH increased from 12% when defined by the 2004 guidelines to 19% when defined by the 2017 guidelines. Overall, the 329 (8%) children who were reclassified to higher blood pressure categories by the 2017 guidelines were more likely than their propensity score-matched normotensive counterparts to develop hypertension, metabolic syndrome, and LVH in later life, whereas 38 (1%) children who were reclassified to lower blood pressure categories by the 2017 guidelines had similar cardiometabolic outcomes to their propensity score-matched normotensive counterparts. Hence, children who were reclassified to higher blood pressure categories based on 2017 guidelines were at increased risk of developing hypertension, metabolic syndrome, and LVH in later life. The 2017 guidelines identified a group of children with adverse metabolic profile and cardiometabolic outcomes, whose cardiovascular risk seemed to be underestimated using the 2004 guidelines.