The 2017 Clinical Practice Guideline (CPG) for the diagnosis and management of pediatric hypertension (PHTN) categorizes a greater proportion of children with elevated blood pressure and PHTN, yet several barriers to CPG adherence have been noted. To assess adherence to the 2017 CPG for the diagnosis and management of PHTN and use of a clinical decision support (CDS) tool to calculate blood pressure percentiles. This cross-sectional study used electronic health record-extracted data from January 1, 2018, to December 31, 2019, among patients visiting 1 of 74 federally qualified health centers in AllianceChicago, a national Health Center Controlled Network. Children and adolescents (aged 3-17 years; hereinafter referred to as children) who attended at least 1 visit and had at least 1 blood pressure reading at or above the 90th percentile or diagnosis of elevated blood pressure or PHTN were eligible for data to be included in the analysis. Data were analyzed from September 1, 2020, to February 21, 2023. Blood pressure at or above the 90th or 95th percentile. Diagnosis of PHTN (International Statistical Classification of Diseases and Related Health Problems, Tenth Revision [ICD-10], code I10) or elevated blood pressure (ICD-10 code R03.0) and CDS tool use; blood pressure management (antihypertensive medication, lifestyle counseling, referral); and follow-up visit attendance. Descriptive statistics described the sample and rates of guideline adherence. Logistic regression analyses identified patient- and clinic-level associations with guideline adherence. The sample consisted of 23 334 children (54.9% boys; 58.6% White race; median age, 8 [IQR, 4-12] years). Guideline-adherent diagnosis was observed in 8810 children (37.8%) with blood pressure at or above the 90th percentile and 146 of 2542 (5.7%) with blood pressure at or above the 95th percentile at 3 or more visits. The CDS tool was used to calculate blood pressure percentiles in 10 524 cases (45.1%) and was associated with significantly greater odds of PHTN diagnosis (odds ratio, 2.14 [95% CI, 1.10-4.15]). Among 15 422 children with blood pressure at or above the 95th percentile, antihypertensive medication was prescribed to 831 (5.4%), lifestyle counseling was provided to 14 841 (96.2%), and blood pressure-related referrals were given to 848 (5.5%). Guideline-adherent follow-up was observed in 8651 of 19 049 children (45.4%) with blood pressure at or above the 90th percentile and 2598 of 15 164 (17.1%) with blood pressure at or above the 95th percentile. Differences in guideline adherence by patient- and clinic-level factors were observed. In this study, fewer than 50% of children with elevated blood pressure had a guideline-adherent diagnosis code or attended guideline-adherent follow-up. Using a CDS tool was associated with guideline-adherent diagnosis, but the tool was underused. Further work is needed to understand how to best support implementation of tools promoting PHTN diagnosis, management, and follow-up.