Cardiovascular disease (CVD) remains a leading cause of morbidity and mortality among older adults. Although the benefits of physical activity are well established in younger populations, evidence in adults aged ≥75 years is limited, particularly in real-world primary care settings. Understanding whether physical activity continues to provide cardiovascular protection in very old adults is highly relevant to family medicine and healthy ageing.To examine the association between weekly physical activity—measured using metabolic equivalents (METs)—and the risk of incident CVD in adults aged ≥75 years, accounting for death as a competing risk.We conducted a nationwide cohort study using the Korean National Health Insurance Service database. A total of 869,524 adults aged ≥75 years who completed health screening between 2012 and 2015 were included after excluding those with previous myocardial infarction, stroke, or missing data. Weekly METs were calculated from standardized questionnaires and categorized into quartiles (Q1=lowest, Q4=highest). The primary outcome was incident CVD (myocardial infarction or stroke). Subdistribution hazard ratios (sHRs) were obtained using competing risk regression models adjusted for demographic, socioeconomic, lifestyle, and clinical factors.Over 5.6 million person-years, 126,686 CVD events occurred. CVD incidence decreased from 20.44 per 1,000 person-years in Q1 to 17.26 in Q4. Higher weekly METs were associated with progressively lower CVD risk (sHR for Q4 vs Q1: 0.84; 95% CI, 0.83–0.85; P for trend <0.001). Regular exercise also reduced CVD risk (sHR 0.86; 95% CI, 0.85–0.88). Cumulative incidence curves showed early and persistent separation across METs quartiles (Gray’s test <0.0001). Subgroup analyses demonstrated consistent associations across sex and comorbidities, with attenuation only among adults aged ≥85 years.Physical activity demonstrated a clear, graded, and clinically meaningful reduction in CVD risk among very old adults. The persistence of benefit up to age 85 highlights the importance of maintaining activity even in advanced age. These findings support primary care interventions promoting safe, sustainable physical activity among older patientsHigher physical activity levels were independently associated with lower CVD risk in adults aged ≥75 years. Physical activity remains a key protective factor in healthy ageing and should be actively encouraged in primary care practice