Semaglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA) known for its glucose-lowering and weight-reducing effects, has been linked to reduced cardiovascular disease (CVD) risk in patients with type 2 diabetes (T2D). However, the impact of semaglutide adherence on CVD events in real-world settings remains unclear. This retrospective observational study analyzed Japanese claims data to investigate the relationship between semaglutide adherence, measured as the proportion of days covered (PDC), and CVD risk in patients with T2D. Good adherence was defined as PDC ≥0.8. The hazard ratio (HR) for CVD incidence in patients with PDC <0.8 was significantly higher than that of those with PDC ≥0.8 (HR: 1.77, 95% confidence interval (CI): 1.25-2.49). Female patients and those taking biguanides exhibited significantly lower HR for CVD (HR: 0.37 and HR: 0.53, respectively). No significant difference in HR was observed based on semaglutide formulation. The incidence of CVD in patients on semaglutide monotherapy with PDC <0.8 tended to be higher than in those with PDC ≥0.8 (HR: 1.56, 95% CI: 0.53-4.57), although no significant difference was found. These findings suggest that maintaining good adherence to semaglutide is important for reducing CVD risk and potentially improving clinical outcomes in patients with T2D, regardless of formulation.