Background There is no agreement about the best reconstructive option following resection of proximal humerus tumors. The purpose of this study was to compare the functional outcomes of endoprosthesis reconstruction versus nail cement spacer reconstruction after wide resection of proximal humeral tumors. Methods This retrospective comparative study included 58 patients with proximal humerus tumors who had undergone tumor resection and reconstruction with modular endoprosthesis (humeral hemiarthroplasties) or cement spacer. Medical records were reviewed for the epidemiological, clinical, radiological, and operative data. Lung metastasis, local recurrence, and complication were also reviewed. The functional outcome was evaluated using the Musculoskeletal Tumor Society scoring (MSTS) system. Results Nineteen patients with a mean age of 33.4 ± 17.5 years underwent reconstruction by modular endoprosthesis, and 39 patients with a mean age of 24.6 ± 14.3 years underwent reconstruction by cement spacer. The mean MSTS score was 24.8 ± 1.1 in the endoprosthesis group and 23.9 ± 1.4 in the spacer group, P = 0.018. Complications were reported in 5 (26.3%) patients in the endoprosthesis group and 11 (28.2%) patients in the spacer group, P = 0.879. There were no statistically significant differences in the functional outcomes in both patient groups with or without axillary or deltoid resection. Conclusions Both endoprostheses and cement spacers are durable reconstructions with almost equal functional outcomes with no added advantage of the expensive endoprosthesis.