Purpose - Given globalization, the new niche market of medical tourism is likely to experience sustainable growth for various reasons, such as aging populations and a shift in the medical consumerism paradigm toward prevention. Importantly, understanding medical customers' behavior is necessary to benefit from a competitive advantage in this industry. The existing research primarily accessed the key factors of medical quality and costs to explain health customers' behavior but is limited in terms of enabling an understanding of the decision process. This limitation exists because, given the intangibility and greater associated risks in the highly professional industry of international medical tourism, most customers lack the knowledge and experience needed to evaluate the central factors-such as the medical competence of health care countries-before purchases. Therefore, they actively search for useful information through various distributions to reduce uncertainty and to make better choices. Interestingly, most of these information channels are associated with word-of-mouth (WOM). However, no evidence is found in the literature to estimate the effect of WOM in the medical tourism field. Thus, this study focuses on WOM to explore its interaction with key medical characteristic factors and the attractiveness of destinations referred to by sources. This study also affects customers' evaluations and, in turn, influences their intention to seek health care services abroad. Research design, data, and methodology - The literature review addressed an interesting research model for estimating the relations among WOM, medical characteristics, attractiveness, and customers' choice intention regarding international health care. In the key economic regions in China, such as Beijing, Shanghai, Jiangsu, Shandong, and Guangdong, 2,500 survey questionnaires were distributed to potential customers of different ages, education, and income levels. A resulting 1,717 (68.68 percent of the original 2,500) usable surveys were obtained for analysis. Moderated regression analysis was used to determine the effects of WOM in the decision process regarding international health care destinations. Results - The results indicate that WOM is a good moderator of the relationships between the factors evaluated by sources and customers. More importantly, the WOM effects reflect the factors of tie strength, credibility, and vividness. The results also reveal that, given the moderating role of WOM, the intention of potential Chinese customers to seek the referred health care country varies according to the medical characteristics of medical competency and reputation as evaluated by customers. In contrast, the travel attractiveness of the attractions, facilities, accessibility, and social environment are critical determinants of destination choice intention. Conclusions - The moderating role of WOM has been confirmed through the international healthcare destination selection process. Medical tourism managers should user WOM as an effective marketing tool for industry development. Specially, marketers should consider the effects of WOM determinants, such as tie strength, credibility, and vividness, to develop an effective strategy. Furthermore, this study estimates the factors that affect customers' selection of medical tourism destinations. Health care managers or policy makers should consider a broad variety of variables that may attract more Chinese customers to international health care.