Background <p>Mediastinal basal pulmonary artery (MPA) variations may increase the risk of unintentional vascular division or excessive bleeding during pulmonary resection. Therefore, precise preoperative anatomical assessment is particularly important.</p> Case presentation <p>We report a rare case of a MPA that was precisely identified preoperatively using three-dimensional computed tomography (3D-CT). Preoperative three-dimensional CT clearly demonstrated an independently branching mediastinal basal pulmonary artery. The patient underwent thoracoscopic left lower lobectomy for primary lung cancer. MPA branched independently from the main pulmonary artery, and division at the ventral interlobar level resulted in the formation of a relatively long arterial stump. The procedure was completed safely without unintentional vascular division, excessive bleeding, or postoperative thrombotic complications.</p> Conclusion <p>Previous reports have described interlobar division of anomalous pulmonary arteries in similar cases. However, the clinical benefit of additional proximal dissection solely to shorten the pulmonary artery stump remains unclear. Unnecessary dissection may increase the risk of bleeding. Careful preoperative anatomical assessment using 3D-CT enables safe surgical management. With expanding indications for segmentectomy, accurate recognition of pulmonary arterial variations will become increasingly important in clinical practice.</p>