The removal of fiber posts for the retreatment of root canals can be challenging. An autonomous robotic (ATR) system was used for accurate and minimally invasive endodontic retreatment in a patient who presented with symptomatic apical periodontitis and pain emanating from the mandibular left first molar, which had been previously restored with 3 fiber posts. Intraoral scanning data, radiographic data, and bur sizes were integrated into preoperative software program to design a treatment plan. The ATR system enabled precise and efficient post removal. The remnant filling material was removed before endodontic retreatment, and radiographs at 3 months after the procedure showed satisfactory healing. This treatment demonstrated the accuracy and efficiency of the ATR system for the removal of fiber posts from pretreated teeth, while minimizing the duration of the procedure and avoiding excessive tissue removal.