This comprehensive review explores the mechanisms and implications of endothelial dysfunction in diabetic vascular complications. Diabetic vascular complications, including macrovascular and microvascular diseases, significantly impact the quality of life and long-term prospects of diabetic patients. Endothelial dysfunction, characterized by increased inflammation, oxidative stress, decreased nitric oxide (NO) biosynthesis, endothelial-mesenchymal transition (EndMT), senescence, and cell death, is a key factor in the progression of these complications. The review delves into the intricate mechanisms driving endothelial dysfunction, such as inflammation, oxidative stress, EndMT, and cell death, and their roles in the development of macrovascular diseases like atherosclerosis (AS) and microvascular diseases like diabetic nephropathy (DN), diabetic retinopathy (DR), diabetic neuropathy (DPN), and cardiomyopathy. The review also discusses the impact of hyperglycemia on endothelial function, highlighting how it leads to impaired vasodilation, increased reactive oxygen species (ROS) production, and disrupted signaling pathways. It further examines the protective effects of various pharmacotherapies, including metformin and dipeptidyl peptidase-4 inhibitors (DPP-4i), which can mitigate endothelial dysfunction and slow the progression of diabetic vascular complications. Despite the benefits, metformin has notable side effects, and DPP-4i inhibitors offer additional benefits beyond their hypoglycemic effects. Overall, the review provides a detailed understanding of the mechanisms underlying endothelial dysfunction in diabetes and highlights the potential of targeted therapies to improve vascular health and reduce the burden of diabetic vascular complications.This comprehensive review explores the mechanisms and implications of endothelial dysfunction in diabetic vascular complications. Diabetic vascular complications, including macrovascular and microvascular diseases, significantly impact the quality of life and long-term prospects of diabetic patients. Endothelial dysfunction, characterized by increased inflammation, oxidative stress, decreased nitric oxide (NO) biosynthesis, endothelial-mesenchymal transition (EndMT), senescence, and cell death, is a key factor in the progression of these complications. The review delves into the intricate mechanisms driving endothelial dysfunction, such as inflammation, oxidative stress, EndMT, and cell death, and their roles in the development of macrovascular diseases like atherosclerosis (AS) and microvascular diseases like diabetic nephropathy (DN), diabetic retinopathy (DR), diabetic neuropathy (DPN), and cardiomyopathy. The review also discusses the impact of hyperglycemia on endothelial function, highlighting how it leads to impaired vasodilation, increased reactive oxygen species (ROS) production, and disrupted signaling pathways. It further examines the protective effects of various pharmacotherapies, including metformin and dipeptidyl peptidase-4 inhibitors (DPP-4i), which can mitigate endothelial dysfunction and slow the progression of diabetic vascular complications. Despite the benefits, metformin has notable side effects, and DPP-4i inhibitors offer additional benefits beyond their hypoglycemic effects. Overall, the review provides a detailed understanding of the mechanisms underlying endothelial dysfunction in diabetes and highlights the potential of targeted therapies to improve vascular health and reduce the burden of diabetic vascular complications.