Background: Complicated crown-root fractures are a type of tooth fracture that involves the enamel, dentin, and cementum and accompanied by pulp exposure. The treatment of a complicated crown-root fracture is always challenging due to the difficulties in achieving a hermetic seal and a stable restoration with a fracture level close to the crestale bone level. This study aimed to evaluate and compare the efficacy of single-visit and multi-visit approaches for fragment reattachment in complicated crown-root fractures of anterior teeth. Methods: Two cohort consist of 10 adolescent patients in each group at both genders, who suffered from permanent anterior tooth complicated crown-root fracture were included. Fragment reattachment with root canal treatment was performed with either single or multiple-visit approach. Single visit fragment attachement combined with root cannel therapy was conducted in single-visit approach group immediately after injury. Fragment attachment, root cananel therapy and post resoration were performed during three times ' clinical visit in multi-visit approach group. Results: All the patients in both groups achieved satisfactory aesthetic results one year after fragment reattachment. Patients who underwent a multi-visit approach had a significantly shorter operative duration, less intra-operative pain and fatigue, slightly better periodontal health at an early stage, and a decreased incidence of temporomandibular joint disorders compared to those who underwent a single-visit approach. However, multiple visits approach may increase the risk of fragment detachment postoperatively. Conclusion: Fragment reattachment a reliable but temporary technique for adolescent patients who have suffered from complicated crown-root fractures. Multi-visit approach showed similar effecacy to single-visit approach but with slightly less complications. The choose of these two merhos should depend on the specific patient situation and patient compliance. Trial registration: This prospective cohort study was retrospectively registered in Chinese Clinical Trial Registry (ChiCTR2300076811) on 19/10/2023.