A detailed understanding of the complexity of root canal systems is imperative to ensure successful root canal therapy. The aim of this study was to evaluate the ability of an optical coherence tomography (OCT) system in imaging root canal walls after endodontic preparation and to correlate these images to histologic sections. Ten extracted mandibular incisors were prepared to size 50 with K-files and Gates Glidden drills. A three-dimensional OCT scan was made with a rotating optical fiber probe inside the root canal. All teeth were sectioned at 5 and 7 mm from the apex and viewed through a microscope. Histologic sections were compared with the corresponding OCT output. All oval canals, uncleaned fins, risk zones, and one perforation that was detected by histology were also imaged by OCT. OCT proves to be a reliable method to image root canals and root dentin in a nondestructive way. This technique holds promise for full in vivo endodontic imaging.