Purpose: The proximal femur is a region frequently affected by pathological fractures due to metastases. Partial head megaprostheses are among the surgical options that can be preferred for treating pathological fractures in this area. The aim of this study is to evaluate the impact of various factors on the functional outcomes and mortality of patients with actual proximal femoral fractures treated with a megaprosthesis. Methods: The study included 28 patients. None of these patients had impending fractures; all of them had actual pathological fractures. Functional outcomes were assessed using VAS improvement, MSTS, and KPS scores, in relation to factors including age, cancer diagnosis before fracture, additional fracture, bone metastasis, visceral metastases, postoperative oncological treatment, preservation of the trochanter major, and type of cancer. These same factors were also considered in the survival analysis. The impact of knowing the cancer diagnosis prior to the fracture on time to surgery was also evaluated. Results: Patients showed a mean VAS improvement of 5.8 ± 1.3, with median postoperative MSTS and KPS scores of 18 (range:12–23) and 65 (range:40–80), respectively. Younger patients had significantly better functional outcomes (p < 0.05). Other clinical factors had no significant effect on functions. Visceral metastases negatively impacted survival (p = 0.044), while younger age (p = 0.029), favorable cancer type (p < 0.001), and receiving postoperative oncological treatment improved survival (p = 0.049). Time to surgery was longer in patients without a prior cancer diagnosis (p < 0.001), though this did not affect survival (p = 0.888). Conclusion: Megaprostheses in the treatment of actual metastatic fractures of the proximal femur provide excellent pain relief and satisfactory functional improvement. Functional outcomes were associated with age, while survival was influenced by age, cancer type, presence of visceral metastases, and whether postoperative oncological treatment was received. Although the preoperative time to surgery was longer in patients without a prior cancer diagnosis, survival was not affected by whether the diagnosis was known before the fracture. Level of Evidence: IV.