Sickle cell disease pathogenesis is a complex interplay of multiple factors associated with vascular endothelial activation, intense oxidative stress, and increased sickle cell adhesion. The aim of this study was to determine and compare three panels of plasma circulating biomarkers at 'steady state' and during veno-occlusive crises (VOC) in a cohort of children and adolescents with SCD and healthy controls. The following biomarkers were assessed: acute phase reactants, endothelial factors, and adhesion molecules. Forty-one SCD pediatric patients and 28 healthy children were enrolled. Patients at 'steady state' presented significantly elevated plasma levels of endothelin-1 (ET-1), soluble-VCAM-1 (sVCAM-1), soluble P-selectin (sP-selectin), and d-dimers compared to the control group. ET-1, sP-selectin, platelet-derived growth factor (PDGF), von Willebrand factor (vWf), d-dimers, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) seems to represent additional, but not independent, prognostic markers of VOC crisis. Elevated plasma levels of sP-selectin, ET-1, and sVCAM-1 were associated with VOC frequency. The present study provides preliminary evidence of a possible association between these biomarkers and the endothelial activation at steady state and VOC in childhood SCD. Further prospective studies are required to confirm the potential independent prognostic value of these markers in different stages of pediatric SCD.