OBJECTIVE : Identifying small lung lesions during minimally invasive thoracic surgery can be challenging. We describe 3D mixed-reality visualization technology that may facilitate non-invasive nodule localization. METHODS : A software application and medical image processing pipeline were developed for the Microsoft HoloLens to incorporate patient-specific data and provide a mixed-reality tool to explore and manipulate chest anatomy with a custom-designed user interface featuring gesture and voice recognition. RESULTS : A needs assessment between engineering and clinical disciplines identified the potential utility of mixed-reality technology in facilitating safe and effective resection of small lung nodules. Through an iterative process, we developed a prototype employing a wearable headset that allows the user to: (1) view a patient's original preoperative imaging, (2) manipulate a 3D rendering of that patient's chest anatomy including the bronchial, osseus, and vascular structures, and (3) simulate lung deflation and surgical instrument placement. CONCLUSIONS : Mixed-reality visualization during surgical planning may facilitate accurate and rapid identification of small lung lesions during minimally invasive surgeries and reduce the need for additional invasive pre-operative localization procedures.