Purpose: Mobile health (mHealth) service is an Australian Government initiative aiming to improve the quality of health-care services. However, little is known about Australian health consumers’ willingness to adopt mHealth. The purpose of this paper is to study the usage behavior of mHealth service users in Australia. While various factors may impact users’ willingness to accept mHealth, this research investigates factors influencing the mHealth adoption decisions of the Australian health-care consumers, and the moderating impact of demographic factors on the usage behavior (UB) of mHealth services which has been rarely addressed in an Australian setting in the past. Design/methodology/approach: The theoretical framework is based on the technology acceptance model (TAM). Data were collected from residents of the Australian Capital Territory using a survey questionnaire and examined using partial least squares structural equation modeling. Findings: The proposed mHealth usage model demonstrated a good fit and indicated that perceived usefulness, perceived ease of use, social influence, service quality and government influence are critical issues shaping mHealth UB. The moderation analysis revealed that users’ demographics, namely, gender, age and education are instrumental in broadening the understanding of UB of mHealth service in Australia. Practical implications: The findings will inform health-care service providers about the critical importance of the key factors driving the usage of mHealth services. Health-care providers and relevant authorities can develop targeted communication strategies that maximize the acceptance of mHealth services. Furthermore, deeper understanding of users’ demographic profiles would enable health-care service providers to promote their services to the right clients. Originality/value: The above findings on the factors and user demographics informing the usage of mHealth services have unique practical, contextual and theoretical implications.