This study was conducted to develop a web-based patients' information management system (PIMS) for Desire Medical Centre, a private health facility in Uganda. The centre had been operating a largely manual, paper-based patient records management system characterized by inefficiency, data loss, and delays in patient service delivery. Using the System Development Life Cycle (SDLC) methodology specifically the structured waterfall model, the study followed iterative phases of requirements analysis, system design, implementation, testing, and deployment. Primary data were collected from 47 healthcare workers including doctors, nurses, records officers, and administrative staff through interviews and structured questionnaires to determine system requirements. Secondary data were gathered from existing patient records and operational documents. The developed system was built using PHP 8.1, MySQL database, HTML5, CSS3, Bootstrap 5 framework, and JavaScript, hosted on an Apache web server. System testing was conducted using black-box and white-box testing techniques. The evaluation revealed that the system achieved a 97.3% task completion rate in usability testing, significantly reduced average patient registration time from 18 minutes to 4 minutes, and improved records retrieval accuracy to 99.1%. The study concludes that the web-based PIMS effectively addresses Desire Medical Centre's patient information management challenges and recommends full deployment, staff training, and regular system maintenance to sustain operational benefits.