Diffuse-type tenosynovial giant cell tumors (Dt-TGCTs) commonly occur in the knee joint and tend to recur postoperatively. However, limited clinical data are available on ankle joint involvement especially associated multiportal arthroscopic treatment outcomes. The purpose of this study was to report the clinical results of multiportal arthroscopy-assisted resection of Dt-TGCTs of the ankle.We retrospectively reviewed the clinical data of 33 patients with Dt-TGCT of the ankle who underwent multiportal arthroscopic treatment between August 2011 and December 2020. Clinical follow-up included the visual analogue scale (VAS) score, American Orthopedic Foot and Ankle Society (AOFAS) score, Kofoed score, and recurrence rate to assess surgical outcomes. The number of patients who achieved the patient acceptable symptom state (PASS) based on the AOFAS score was also examined. Additionally, the patients were categorized into two groups based on the final surgical approach: Group A who underwent multiportal arthroscopic synovectomy and Group AO who underwent combined arthroscopic and open surgical excision. Intergroup comparisons were conducted. Intraoperative characteristics, such as the number of patients with involvement of the tarsal tunnel and fibularis tendon and the Outerbridge grading of cartilage damage, were recorded to assess the selection of surgical procedures.Among the 33 patients, 15 were assigned to Group A, and 18 were in Group AO. The median follow-up duration for the 33 patients was 77 months (range, 28-142 months). The median VAS score was 1 (range, 0-4), the AOFAS score was 96 (range, 65-100), and the Kofoed score was 96 (range, 67-100). A total of 27 patients (82%) achieved PASS based on AOFAS scores, while five patients (15%) had recurrence. No statistically significant difference was observed between the two groups in recurrence rate, follow-up VAS score, AOFAS score, Kofoed score, or number of patients who reached the PASS (p > 0.05). In the AO group, 16 cases of Dt-TGCT involved the tarsal tunnel, and 11 cases involved the fibularis tendon. All these patients exhibited extension beyond the joint. In contrast, only one patient in Group A had involvement of the tarsal tunnel. Statistically significant differences were observed between the groups (p < 0.001).This study demonstrated that, with the assistance of a multiportal arthroscopic approach, surgical excision of Dt-TGCT in the ankle resulted in favorable clinical outcomes with a relatively low recurrence rate. Additionally, patients with extra-articular involvement were more likely to require concomitant open surgery.© 2024 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.