Sickle cell disease (SCD) is a hereditary hemoglobinopathy that affects over 100,000 people in the United States. Patients with SCD are known to experience suboptimal health-related quality of life (HRQoL). In addition to the physical manifestations of SCD, psychological and social stress, along with academic difficulties, secondary to the chronicity of the disease and its complications often affect patients with SCD. Although medical therapy of SCD has improved, allogeneic hematopoietic cell transplantation (allo-HCT) remains the only curative therapy. The objective of this study was to measure HRQoL before and after allo-HCT by assessing physical, psychological, and social functioning in patients with SCD who have undergone reduced-toxicity conditioning (busulfan/fludarabine/alemtuzumab) followed by allo-HCT. Patients < 21 years of age undergoing allo-HCT (matched siblings and unrelated donors) for SCD and their primary caregiver were enrolled using either the English or Spanish version of the PedsQoL 4.0. Data were collected at 3 time points: before allo-HCT and on days 180 and 365 after allo-HCT. The change in HRQoL from baseline was assessed with unadjusted and adjusted mixed-effects models in which subjects were treated as random effects, and variance component structure was used. Seventeen patients and 23 primary caregivers were enrolled and reported a mean overall HRQoL of 66.05 (SD, 15.62) and 72.20 (SD, 15.50) at baseline, respectively. In the patient-reported analysis with adjusted mixed-effects models, the estimated improvements in overall HRQoL were 4.45 (SE, 4.98; P = .380) and 16.58 (SE, 5.06; P = .003) at 180 and 365 days, respectively, after allo-HCT. For parent-reported overall HRQoL, the estimated improvements were 1.57 (SE, 4.82; P = .747) and 9.28 (SE, 4.62; P = .053) at 180 and 365 days, respectively, after allo-HCT. Similar results were found across the physical, social, and emotional HRQoL domains with mixed-effects models after adjustment of demographic and medical variables. In addition to the alleviation of clinical manifestations of SCD, these patients demonstrated significant improvement in most aspects of HRQoL by 1 year after allo-HCT. These data represent the trajectory of HRQoL during the initial year of follow-up within this population and should be integrated into the decision-making process when considering allo-HCT in patients with SCD.