Persistent left superior vena cava (PLSVC) is one of the most common thoracic venous anatomical anomalies and poses challenges in establishing central venous access. This report describes a patient with advanced breast cancer complicated by type I PLSVC who successfully underwent venous access port implantation via the left subclavian vein under digital subtraction angiography (DSA) guidance. Intraoperative DSA clearly demonstrated the abnormal venous pathway, and electrocardiographic monitoring was combined to accurately position the catheter tip at the middle-to-lower third of the left superior vena cava, resulting in successful port implantation. After a 104-day follow-up period, the venous access port functioned well, and no catheter-related complications were observed. These findings indicate that DSA guidance allows real-time identification of venous anatomical variations and precise evaluation of catheter position, thereby improving the safety and success rate of venous access port implantation in patients with PLSVC and providing a reliable method for establishing long-term venous access in such patients.