Background <p>Metastatic lesions of the proximal femur frequently result in severe pain, impaired mobility, and pathological fractures. Surgical intervention aims to restore skeletal stability, allow early mobilization, and improve quality of life. This study compared clinical, functional, and quality-of-life outcomes following endoprosthetic reconstruction (arthroplasty) versus intramedullary osteosynthesis in patients with metastatic proximal femoral disease.</p> Methods <p>This single-center observational cohort study included 54 patients treated with either arthroplasty (<i>n</i> = 27) or intramedullary nail osteosynthesis (<i>n</i> = 27). Outcomes were assessed at 30 days, 6 months, and 12 months and included time to mobilization, SF-36 quality-of-life domains, the Bodily Pain score, functional mobility categories, Harris Hip Score (HHS), and postoperative complications.</p> Results <p>Arthroplasty enabled significantly earlier mobilization (2.0 ± 0.79 vs. 5.7 ± 0.90 days; <i>p</i> &lt; 0.001) and superior pain control (SF-36 Bodily Pain: 90 vs. 33; <i>p</i> &lt; 0.001). Functional recovery was consistently better following arthroplasty, with higher independent ambulation rates and significantly higher HHS values at all follow-up points (12-month HHS: 78 ± 12 vs. 68 ± 16; <i>p</i> &lt; 0.01). All SF-36 domains demonstrated statistically significant improvement in the arthroplasty group (all <i>p</i> &lt; 0.001). Although overall complication rates were comparable (30 vs. 33 events), osteosynthesis showed a higher frequency of mechanical failures.</p> Conclusion <p>Endoprosthetic reconstruction was associated with earlier mobilization, improved pain control, better functional recovery, and higher quality-of-life scores compared with osteosynthesis in this cohort. These findings suggest that arthroplasty may represent a reliable reconstructive option for appropriately selected patients with metastatic lesions of the proximal femur.</p>