Vascular endothelial senescence is an important pathophysiological factor in the development and exacerbation of cardiovascular health problems linked to diabetes mellitusn (DM). Accumulating evidence confirms that 1,8-cineole has multiple pharmacological properties, including anti-inflammatory, anti-microbial, and antioxidant activities. We investigated whether 1,8-cineole could ameliorate cardiovascular diseases and endothelial dysfunction, as the pharmacological properties and mechanism of diabetic vascular ageing remain unknown. Our results revealed notable senescence biomarkers in both in vivo and in vitro models. Treatment with 1,8-cineole alleviated lipid profiles and vascular senescence in mice with DM. Additionally, bioinformatics analysis suggested that peroxisome proliferator-activated receptor-γ (PPAR-γ) plays a crucial role in DM and ageing. We confirmed the binding capacity PPAR-γ with 1,8-cineole. Accordingly, experiments with the PPAR-γ agonist rosiglitazone, the PPAR-γ inhibitor GW9662, and PPAR-γ siRNA were performed to validate the pharmacological characteristics of 1,8-cineole. Finally, we clarified that 1,8-cineole can directly target PPAR-γ protein, as verified by cellular thermal shift assay, drug affinity responsive target stability, and surface plasmon resonance analyses. Taken together, these results provide the first evidence that 1,8-cineole ameliorates DM-induced vascular endothelial ageing via stabilising PPAR-γ protein by promoting deubiquitination at the Lys-466 site.