Mitochondria are dynamic organelles altering their inner and outer membranes through fission and fusion mechanisms. In response to shear stress, the mitochondria in endothelial cells (ECs) continuously undergo fusion and fission mechanisms. We hypothesized that alteration in mitochondrial dynamics could alter ECs function leading to vascular damages. For that, we investigated the role of OPA1 and DRP1 deficiency in ECs and vascular homeostasis using mice lacking fusion protein OPA1 and fission protein DRP1(heterozygous Opa1±& Drp1±mice). We investigated mitochondrial dynamics-related proteins expression level in ECs submitted to a disturbed shear stress (evidenced by eNOS down-regulation and endothelin-1 up-regulation) and observed a reduction in fusion protein OPA1 mRNA expression and an increase in fission protein DRP1 mRNA expression level. The opposite was observed in ECs submitted to disturbed shear stress. After acute stimulation of ECs to Histamine, cells lacking OPA1 and DRP1 protein have shown a decreased intracellular Ca2+ release, compared to control cells. Besides, these cells showed a decreased capability of migration compared to control cells. As shear stress determines atherogenesis in large arteries, we investigated mitochondrial dynamics-related proteins in various areas in the mouse aorta. In the areas submitted to low shear stress (inner part of the aortic cross), OPA1 mRNA expression was reduced and DRP1 mRNA expression was increased compared to aortic areas subjected to high shear stress. These observations led to investigate atherosclerosis in Opa1± and Drp1±mice. These mice, when crossed with Ldlr−/− mice and fed high fat diet, develop more atherosclerosis in Opa1±and less in Drp1±mice compared to WT. Thus, disregulation in mitochondrial dynamics proteins altered endothelium dependent functions in atherosclerotic mice, and increasing plaque formation with reduced fusion.