Introduction: Sickle cell disease is an inherited hemoglobinopathy with defective red cell deformability. The defective deformability promotes microvascular occlusion and subsequent vaso-occlusion in sickle cell disease patients. Previous studies have demonstrated that thiol isomerases, an endoplasmic reticulum-resident oxidoreductase that is released from vascular cells into the bloodstream, are present on red cell membrane and contribute to cellular dehydration and sickling. However, the role of membrane-bound thiol isomerases on sickled red blood cells is unclear. Methods: Using red blood cells from Townes humanized sickle cell or non-sickled mice, we performed ektacytometry assay under shear using laser assisted optical rotational cell analyzer (LORRCA) to assess the effects of antagonizing thiol isomerases with isoquercetin and a functional blocking monoclonal antibody. The densitometric properties of sickled red blood cells in the presence of isoquercetin was also tested using magnetic levitation. Results: Thiol isomerase antagonism increased sickled red cell elongation, cellular dehydration and the diamagnetic signature compared to control treatment. Conclusion: Thiol isomerases may be involved in regulating sickled red blood cells mechanical properties through mechanisms that require further investigation.