With the rapidly growing popularity of the delivery of health services through the Internet, it is timely to examine online health service (OHS) diffusion from the human decision process perspective for its development and diffusion. The health service possesses an offline-to-online nature; that is, its online service is an extension of its offline service. Therefore, we develop a research model to bridge offline healthcare and the OHS-decision, which is contingent on different levels of offline healthcare habits, drawing on user satisfaction literature, the Innovation Diffusion Theory, and the habit literature. Data were collected from 323 Internet users, and our empirical results show that high satisfaction on offline healthcare hinders the awareness of OHS and subsequently influences adoption intention. On the other hand, offline healthcare habits weaken the effects of offline health satisfaction on the OHS awareness. Discussions and implications are also proposed in the concluding sections of this research.