Background: Prosthetic reconstruction after periacetabular tumor resection likely yield good function. However, complications with this technique are common. Therefore, alternative prosthetic design and surgical technique warrant study. Methods: Six patients were retrospectively reviewed with malignant periacetabular tumors who received reconstruction using 3D-printed prostheses assisted by osteotomy guide plates via two approaches between July 2017 and June 2020. The surgical data, including operative duration and intraoperative blood loss were recorded. Preoperative and postoperative pain at rest was examined using the visual analog scale (VAS). The postoperative functional outcomes were evaluated using the Musculoskeletal Tumor Society (MSTS) scoring system, and the postoperative complications were analyzed.Results: The mean follow-up was 19 months (range, 3-36 months). The mean intraoperative blood loss was 1416 ml (range, 600-2000 ml), and the mean operative duration was 333 min (range, 300-370 min). Satisfactory surgical margins were achieved in all patients. Six patients complained of severe pain preoperatively (VAS score, mean, 6; range, 4-8) and described significant alleviation of pain at 4 weeks postoperatively (VAS score, mean, 2; range, 0-5). At the 12 weeks after surgery, the mean MSTS score was 15.6 (range, 5-27). Local recurrence occurred in one patient at 3 months after surgery.Conclusions: The 3D-printed prosthesis represents a potential alternative for reconstruction after malignant periacetabular tumor resection. The design of the two approaches and the use of osteotomy guide plates can yield good functional results, as well as low rate of complications.Trial registration: This study has been granted an exemption from requiring ethics approval by the ethics committee of Tianjin Hospital.