Medical self-service terminals (MSTs) offer potential advantages for optimizing workflows and enhancing patient experience in hospitals, particularly for the elderly. Despite this, the uptake of MSTs among older adults in China remains a challenge. This research aims to identify the key factors influencing behavioral intention (BI) to adopt MSTs in this age group, with a particular emphasis on user interface (UI) attributes. We extend the Unified Technology Acceptance and Use Theory (UTAUT) model to include these UI elements. Our empirical analysis examines seven variables, which include three critical UI attributes and four core UTAUT elements. The results highlight the importance of performance expectancy (β = 0.40, p < 0.001), effort expectancy (β = 0.50, p < 0.001), and social influence (β = 0.25, p < 0.05) in shaping BI. Importantly, the design of the user interface shows a strong positive correlation with both performance expectancy (β = 0.89, p < 0.001) and effort expectancy (β = 0.81, p < 0.001). These findings illuminate the complex relationship between objective UI features and subjective UTAUT factors. Our study enriches the understanding of how UI design affects the willingness and acceptance of MSTs, especially among China’s elderly population, emphasizing the need to incorporate their viewpoints for successful technology integration in healthcare.