Background <p>Hypertension remains one of the most prevalent modifiable risk associations for adverse outcomes in children receiving dialysis. Despite this, limited longitudinal data exist regarding ambulatory blood pressure monitoring (ABPM) and cardiac outcomes in children and young people (CYP) initiating dialysis.</p> Methods <p>This is a retrospective, longitudinal study of CYP age 5–18 with paired echocardiogram and ABPM evaluations over 12 months (“baseline” to “follow-up”) following dialysis initiation. Left ventricular hypertrophy (LVH) was defined by age-specific indexed left ventricular mass (LVMI) and LV mass-for-height z-score ≥ 95th percentile. Hypertension was defined if day, night, or 24-h ABPM ≥ 95th percentile and CYP was categorised as having persistent hypertension, resolved hypertension, persistent normotension, or emergent hypertension.</p> Results <p>There were 32 CYP, with a mean age of 12.7 ± 3.1&#xa0;years. LVH was present in 37.5% at baseline and 25% at follow-up. LVH rates improved on haemodialysis (baseline 52.9%, follow-up 17.6%, <i>P</i> = 0.031), but not on peritoneal dialysis. Higher rates of hypertension were found in LVH versus no LVH at follow-up. Masked hypertension rates was present in 14 (43.8%)&#xa0;at both&#xa0;baseline and follow-up. Mean LVMI was higher in persistently hypertensive versus persistently normotensive CYP at follow-up. ΔLVMI was independently associated with LVH at baseline (yes/no) (<i>β</i> = −0.482, <i>P</i> = 0.001), and Δlog N-terminal pro-brain b-type natriuretic peptide (NT Pro-BNP) (<i>β</i> = 0.412, <i>P</i> = 0.005).</p> Conclusions <p>CYP with persistent hypertension had worst rates of LVH and indexed LV mass. A correlation between changes in NT Pro-BNP and LVMI highlights a probable role of fluid overload. Further research into using NT Pro-BNP as a biomarker to improve hypertension management is warranted.</p> Graphical abstract <p></p>