BACKGROUND: Wearable devices with heads-up displays or smart glasses can overlay images onto the sight of the wearer. This technology has never been applied to surgical navigation. OBJECTIVE: To assess the applicability and accuracy of smart glasses for augmented reality (AR)-based neurosurgical navigation. METHODS: Smart glasses were applied to AR-based neurosurgical navigation. Three-dimensional computer graphics were created based on preoperative magnetic resonance images and visualized in see-through smart glasses. Optical markers were attached to the smart glasses and the patient's head for accurate navigation. Two motion capture cameras were used for registration and continuous monitoring of the location of the smart glasses in relation to the patient's head. After the accuracy was assessed with a phantom, this technique was applied in 2 patients with brain tumors located in the brain surface. RESULTS: A stereoscopic view by image overlay through the smart glasses was successful in the phantom and in both patients. Hands-free neuronavigation inside the operative field was available from any angles and distances. The targeting error in the phantom measured in 75 points ranged from 0.2 to 8.1 mm (mean 3.1 ± 1.9 mm, median 2.7 mm). The intraoperative targeting error between the visualized and real locations in the 2 patients (measured in 40 points) ranged from 0.6 to 4.9 mm (mean 2.1 ± 1.1 mm, median 1.8 mm). CONCLUSION: Smart glasses enabled AR-based neurosurgical navigation in a hands-free fashion. Stereoscopic computer graphics of targeted brain tumors corresponding to the surgical field were clearly visualized during surgery.