The purpose of this study, entitled “Factors Influencing Library User’s Acceptance of Online Electronic Database, Faculty of Medicine, Chiang Mai University,” was to 1) study the factors affecting a library user’s acceptance of the online electronic database at Chiang Mai University’s Faculty of Medicine, and 2) to study the level of acceptance of that database. The study’s sample group comprised 343 professors, medicos and paramedics of the Faculty of Medicine, Chiang Mai University, and involved quantitative research. The data were collected by using a survey questionnaire developed under the Unified Theory of Acceptance and Use of Technology (UTAUT) and collected using quota sampling. The data were analyzed by frequency, percentile, mean, and standard deviation. The study’s hypothesis was tested through multiple regression, sample regression and an independent-samples t-test. The findings reveal that both performance and effort expectancies were related to usage intention, while social influence and gender were not. Age, experience and voluntariness affected usage intention. Facilitating conditions had a relationship and effect on use behavior, which was also affected by usage intention.