Background <p>Venous air embolism (VAE) is a rare but potentially fatal complication in neurosurgery typically caused by injury to dura mater, especially venous sinuses, during craniotomy. We report two cases of VAE that occurred before dural incision.</p> Case presentation <p>Both patients underwent craniotomy under general anesthesia in a head-up position. Hemodynamic and respiratory deterioration occurred during or immediately after burr hole drilling with abnormal vital signs and transesophageal echocardiography findings, raising suspicion for VAE. Immediate management, including surgical field protection and cardiopulmonary support, stabilized the patients’ conditions. The procedure was subsequently discontinued in case 1 and modified to limited resection in case 2. Postoperative computed tomography revealed intracranial venous air within the internal jugular vein, cavernous sinus, and diploic veins.</p> Conclusion <p>These cases highlight that VAE can occur even before dural incision. Vigilant intraoperative monitoring and prompt intervention are essential for preventing potentially fatal outcomes.</p>