Background: Osteoporotic proximal humerus fractures pose significant challenges due to reduced bone quality and healing potential. PHILOS plates offer angular stability, but long-term prospective outcome studies are limited. Objective: To prospectively evaluate the efficacy of PHILOS plates in managing osteoporotic proximal humerus fractures, focusing on functional recovery, complication rates, and patient satisfaction. Methods: This prospective study was conducted at the Department of Orthopaedic Surgery, North East Medical College, Sylhet, also with multicentered study from June 2022 to July 2024, involving 358 patients with osteoporotic proximal humerus fractures. Patients underwent open reduction and internal fixation using PHILOS plates. Functional outcomes were assessed using the Constant-Murley Score (CMS) and DASH score at 6, 12, and 18 months postoperatively. Complications, including screw perforation and avascular necrosis, were systematically recorded. Data analysis included mean score changes, percentages, and ANOVA for repeated measures. Results: The study reported a 94% follow-up rate. At 18 months, 83.5% of patients achieved good to excellent outcomes based on CMS. The mean CMS improved from 30.2 preoperatively to 76.8 at 6 months, 81.4 at 12 months, and 83.9 at 18 months (p < 0.001). The DASH score significantly decreased from 58.1 to 18.5 over 18 months. Complication rates included screw perforation in 6.7%, avascular necrosis in 5.3%, and hardware failure in 4.2%. Patients <70 years showed a mean CMS of 86.1 compared to 77.5 in older patients (p = 0.02). Conclusion: PHILOS plates provide reliable fixation for osteoporotic proximal humerus fractures, yielding excellent functional outcomes and manageable complication rates in a prospective setting.