Twenty-First Century Education is a design of instructional culture that empowers learner-centered through the philosophy of "Less teaching but more learning". Due to the development of technology enhance learning in developing countries such as Thailand, online learning is rapidly growing in the electronic learning market. ClassStart is a learning management system developed to support Thailand's educational management and to promote the student-centred learning processes. It also allows the instructor to analyse individual learners through system-generated activities. The study of online learning acceptance is primarily required to successfully achieve online learning system development. However, the behavioural intention of students to use online learning systems has not been well examined, in particular, by focusing specific but representative applications such as ClassStart in this study. This research takes the usage of ClassStart as research scenario and investigates the individual acceptance of technology through the Unified Theory of Acceptance and Use of Technology, as well as technological quality through the Delone and McLean IS success model. A total of 307 undergraduate students using ClassStart responded to the survey. The Partial Least Squares method, a statistics analysis technique based on the Structural Equation Model (SEM), was used to analyze the data. It was found that performance expectancy, social influence, information quality and system quality have the significant effect on intention to use ClassStart. Keyword: ClassStart, Unified Theory of Acceptance and Use of Technology (UTAUT), Delone and McLean IS, Thailand.