Nigeria's district hospitals play a crucial role in providing essential healthcare services across diverse geographical regions. However, their operational and clinical effectiveness vary significantly, necessitating systematic assessments. A mixed-methods approach was employed, combining quantitative data analysis via regression models and qualitative insights from interviews. Data were collected from 20 randomly selected district hospitals across Nigeria over a two-year period. Regression analyses revealed an average $R^2$ of 75% for explaining clinical outcomes variability, indicating moderate explanatory power of the hospital systems on patient care effectiveness. The quasi-experimental design provided robust evidence to support the hypothesis that effective district hospitals can significantly improve clinical outcomes. Future research should explore long-term sustainability and scalability of these findings. District health authorities are encouraged to adopt system-wide improvements based on this study's recommendations, particularly in enhancing referral processes and training healthcare providers.