This paper assesses the acceptance and use of IoT–based healthcare services, a growing field driven by the rapid evolution of digital technologies in the healthcare sector. Drawing on the Unified Theory of Acceptance and Use of Technology (UTAUT) and complementary empirical models, this study investigates the impact of various factors on users’ willingness to adopt and use IoT services. A structured questionnaire was distributed to 225 respondents aged 18 to 65 who had experience using IoT–based health services. The collected data were analyzed using Structural Equation Modeling (SEM) to test seven hypotheses. The findings show that performance expectancy, effort expectancy, social influence, and facilitating conditions significantly promote IoT adoption, while perceived risk inhibits it. Surprisingly, financial cost did not significantly affect adoption in the Vietnamese context. Furthermore, behavioral intention (IoT adoption) was found to be a strong predictor of actual usage behavior. These insights extend the theoretical boundaries of UTAUT by incorporating context–specific variables and provide practical implications for healthcare providers, technology developers, and policymakers aiming to increase the effectiveness and reach of smart health solutions.