Background Diabetic retinopathy (DR) is a major complication of diabetes mellitus, characterised by retinal vasculopathy and oxidative stress. Semaglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA), has demonstrated cardiovascular benefits but has also been associated with mixed effects on DR progression. This study investigates the potential of semaglutide to attenuate DR progression by ameliorating retinal vasculopathy and oxidative stress in both in vivo and in vitro models.Methods In vivo, a streptozotocin-induced DR rat model was used, and semaglutide (100 mu g/kg/week) was administered for 5 weeks. The retinal pathological symptoms, vascular lesions, neuronal apoptosis, and inflammation were evaluated by HE staining, PAS staining, immunohistochemistry staining, and ELISA assay. In vitro, human retinal microvascular endothelial cells (HRMECs) exposed to a high glucose (HG) environment were treated with semaglutide (5 nM) to assess oxidative stress, vascular endothelial conditions, and inflammation by immunofluorescence and ELISA assay.Results Semaglutide significantly reduced the blood glucose levels of DR rats and improved their retinal function. It increased the thickness of the inner nuclear layer of the retina and alleviated neuronal apoptosis. Semaglutide also alleviated retinal vascular lesions and inflammatory responses, which were demonstrated by the increase in retinal vascular tight junction markers and the reduction in pro-inflammatory cytokines. In high glucose-treated HRMECs, semaglutide inhibited oxidative stress and cellular inflammation, and simultaneously downregulated the expression of VFGFA. In the semaglutide-treated group, the expression of ZO-1 was restored.Conclusion Semaglutide slows the progression of diabetic retinopathy by improving retinal vascular lesions and reducing oxidative stress. Its mechanism of action may involve the reduction of inflammation and apoptosis. Its overall protective effect on retinal function and oxidative stress highlights its potential as a therapeutic drug for diabetic retinopathy. Further mechanisms and clinical studies are needed to validate these findings and assess the long-term effects.