Hospital disaster preparedness is essential for ensuring continuity of healthcare services and minimizing the impact of emergencies and disasters. Despite the availability of national disaster preparedness guidelines, hospitals face challenges in maintaining comprehensive and up-to-date preparedness systems. This study evaluated disaster preparedness at District General Hospital Matara, Sri Lanka, identified key operational challenges, and proposed evidence-based strategies to strengthen organizational resilience. A descriptive case study design was employed using methodological triangulation. Data were collected through document review, key informant interviews, direct observations, and assessment using a structured checklist adapted from the World Health Organization Hospital Emergency Response Checklist and national disaster preparedness guidelines. The checklist comprised 43 indicators across 12 preparedness domains. A study-specific Composite Hospital Disaster Preparedness Score (CHDPS) was developed to summarize preparedness across organizational domains. Operational challenges were prioritized using the Nominal Group Technique, and the highest-priority problem was further analysed through root cause analysis to identify underlying organizational factors. The overall CHDPS was 74.4% (64/86). The highest preparedness scores were observed in Recovery and Termination (100%), External Coordination (83.3%), Security and Access Control (83.3%), and Notification and Activation (80.0%). Lower preparedness scores were identified in Staff Mobilization and Welfare (60.0%), Triage and Patient Management (62.5%), and Debriefing and Quality Improvement (66.7%). The principal operational challenge was an outdated Hospital Disaster Preparedness and Response Plan, with root causes related to governance, organizational processes, human resources, and monitoring mechanisms. The study demonstrates that structured preparedness assessment combined with quality improvement methodologies can effectively identify institutional strengths and operational gaps. The proposed CHDPS provides a practical framework for monitoring hospital disaster preparedness and supporting continuous organizational improvement. The findings offer practical guidance for strengthening disaster preparedness and enhancing health system resilience in Sri Lanka and other comparable resource-constrained