This study examined the relationship between Hospital Information Systems (HIS) and healthcare service delivery in public hospitals in Uganda, focusing on Entebbe Regional Referral Hospital and Dr. Ronald Bata Hospital. The research aimed to assess the extent of HIS implementation, determine the impact of electronic medical records (EMRs) on service delivery, and identify challenges hindering effective HIS utilization. The problem addressed was the suboptimal healthcare outcomes linked to inefficient information management. The study was grounded in the Technology Acceptance Model (TAM) and the DeLone and McLean Information Systems Success Model (ISSM). TAM was applied to evaluate healthcare workers' perceptions of HIS usefulness and ease of use, while ISSM provided a framework to assess system quality, information quality, and user satisfaction. These theories helped to analyze both individual acceptance and organizational factors influencing HIS adoption. A mixed-methods approach was employed, combining quantitative data from structured questionnaires administered to 212 healthcare staff and qualitative insights from semi-structured interviews with key informants. Findings for each objective revealed: Objective one HIS implementation was significant but utilization was inconsistent, with regression analysis confirming its positive influence on service delivery (β = 0.265, p < 0.001). Objective two Electronic Medical Records (EMRs) demonstrated the strongest positive relationship with service delivery (β = 0.419, p < 0.001), enhancing data accuracy and patient care. Objective three Challenges including staff resistance and technical failures significantly hindered system effectiveness (β = 0.271, p < 0.001). The study concludes that while HIS and EMRs substantially improve healthcare delivery, their full potential is unrealized due to persistent implementation barriers. Recommendations include investing in robust infrastructure to support implementation, enhancing EMR systems to maximize their impact, and implementing comprehensive change management strategies to address user resistance. These measures are essential to leverage the demonstrated