Previous studies have investigated cardiovascular disease (CVD) risks in cancer patients, but there is limited knowledge concerning the CVD risk in adult and young adolescent (AYA) survivors of gastric cancer. This study aims to investigate the incidence of CVD in AYA gastric cancer survivors, analyzing it by treatment type and identifying associated risk factors. We conducted a retrospective cohort study using Korean National Health Insurance Service data collected from 2006 to 2019. Propensity score matching (1:3, caliper < 0.1) was performed using the variables age, sex, income, residential area, and presence of comorbidities, and we classified participants into gastric cancer (n = 6562) and non-cancer control (n = 19,678) groups. Cox regression models were used to calculate hazard ratios (HRs) for CVD incidence. The study assessed CVD incidence by cancer treatment and identified risk factors through multivariable Cox regression. During a median 6.5-year follow-up, AYA gastric cancer survivors consistently exhibited greater CVD incidence. Their risk of CVD was significantly elevated compared to that of controls (HR, 1.18; 95% confidence interval [CI] 1.05-1.33). In particular, deep vein thrombosis (HR, 3.93; 95% CI 3.06-14.67) and pulmonary embolism (HR, 6.58; 95% CI 3.06-14.67) risks were notably increased. Chemotherapy was associated with an increased risk of stroke, heart failure, atrial fibrillation, deep vein thrombosis, and pulmonary embolism. Hypertension (HR, 1.58; 95% CI 1.10-2.26) and dyslipidemia (HR, 1.46; 95% CI 1.06-2.20) emerged as risk factors for CVD development. This study reports elevated risks of CVD in AYA gastric cancer survivors and emphasizes the need for vigilant monitoring of CVD in this population.