Aim and objective: The aim of this case report was to describe regenerative endodontic procedures (REPs) of the previously treated mature teeth with long-term results. Background: Regenerative endodontic procedures are aimed to treat apical periodontitis and regenerate the pulp–dentin complex in necrotic teeth. However, there is no consensus in using REPs in the previously treated mature teeth. The aim of this case report was to describe REPs of the previously treated mature teeth with long-term results. Case description: A 25-year-old woman presented pain on chewing on 15 and swelling (WHO numbering system). The tooth had been endodontically treated and restored 4 years ago. After removing the old root canal filing, the roots were irrigated with 2.5% sodium hypochlorite and 17% EDTA using sonic activation. Calcium hydroxide (CH) was used as medicament for 3 weeks. At the second visit, CH was removed, and canals were irrigated as like as the first visit. Apical bleeding was induced, and concentrated growth factors (CGFs) were placed inside the root canal. The tooth has been followed up to 3 years. Conclusion: The tooth was functional and asymptomatic at the recall visits. Since the first-year follow-up, the tooth responded to the electric pulp test and the thermal test. Radiological examinations revealed healing of apical lesion and hard tissue deposition. Clinical significance: Regenerative endodontic procedures can offer an advantage over traditional endodontic procedures in terms of tertiary healing, with a predictable, user-friendly procedure also for retreatment cases.