Diabetic retinopathy (DR) is the most common microvascular complication of diabetes mellitus (DM). Key drivers of DR include mitochondrial dysfunction, oxidative stress, and chronic inflammation, which lead to premature senescence of cells within the retinal vasculature. Senolytics improve outcomes in both animal models and in patients with severe forms of DR. In this review, we discuss (i) the role of endothelial senescence in each stage of DR pathogenesis, (ii) methods for detecting senescence in cultured endothelial cells and retinal vessels, and (iii) potential mechanistic explanations for how cells within retinal vessels resist DM-driven senescence.