Background <p>Many individuals with sickle cell disease (SCD) survive into adulthood, posing a challenge in managing and preventing damage to vital organs such as the heart and kidneys. Studies on hypertension in this population have shown conflicting results, and limited studies on polysomnography highlight a gap in research. This study aims to investigate the prevalence of ambulatory blood pressure abnormalities, obstructive sleep apnea (OSA), and end-organ damage in these children and examine the relationship between these factors.</p> Methods <p>Fifty-nine children aged 5–18&#xa0;years with SCD (homozygous and compound heterozygous) were evaluated through history, laboratory tests, ambulatory blood pressure monitoring (ABPM), and polysomnography; estimated glomerular filtration rate (eGFR) by creatinine and cystatin C, echocardiography including left ventricular mass index (LVMI), carotid intimal medial thickness (CIMT), and flow-mediated dilation (FMD) were also assessed.</p> Results <p>Ambulatory hypertension, masked hypertension, and non-dipping pattern were observed in 13.6%, 11.9%, and 66.1% of participants, respectively. End-organ damage was noted in 71% and was associated with higher frequency of vaso-occlusive crisis (<i>p</i> = 0.003). OSA was identified in 66.1% of participants, and they had lower hemoglobin (<i>p</i> = 0.004). Higher CIMT and LVMI <i>Z</i>-scores were observed in children with OSA (<i>p</i> = 0.004 and <i>p</i> = 0.016, respectively). A negative correlation was observed between FMD and apnea–hypopnea index (AHI) (<i>p</i> = 0.009). Proteinuria was reported in 32.2% and AHI correlated significantly with urine protein–creatinine ratio (<i>r</i> = 0.3; <i>p</i> = 0.02). Although eGFR by both methods showed poor correlation, agreement improved at lower eGFR.</p> Conclusions <p>Children with SCD show a high prevalence of ABPM abnormalities, OSA, and early vascular dysfunction.</p> Graphical abstract <p></p>