Intracanal separation of nickel titanium files hinders complete shaping, cleaning, and filling of the root canal system and ultimately influences the endodontic treatment outcome. In this case report, we presented a successful broken instrument retrieval from the middle third of the mesiobuccal root canal of tooth #30 with the assistance of cone-beam computed tomograpgy based preoperative computer-assisted simulation, micro-trepan bur and micro-tube from Micro-Retrieve & Repair system and dental operative microscope. The involved tooth was then successfully cleaned, shaped and obturated followed by coronal restoration. At the three-year follow-up, tooth #30 was asymptomatic and functioned well without radiographic changes. The present case provides an example to show the robustness of computer-assisted technology in dental procedures and to show how the combination of advanced techniques can facilitate root canal therapy.