Background Social media has become one of the primary information sources for medical professionals and patients. Pharmaceutical companies are committed to using various social media platforms to provide stakeholders with digital medical information services (DMISs), which remain experimental and immature. In China, WeChat tops the list of popular social media platforms. To date, little is known about the service model of DMISs delivered by pharmaceutical companies via WeChat. Objective This study aims to explore the emerging service model of DMISs delivered by pharmaceutical companies via WeChat in China. Methods This study applied a qualitative research design combining case study and documentary analysis to explore the DMISs of 6 leading pharmaceutical companies in China. Materials were collected from their official WeChat platforms. Thematic analysis was conducted on the data. Results The DMISs of 6 pharmaceutical companies were investigated. Themes emerged regarding 2 essential information services delivered by pharmaceutical companies via WeChat: business operation services and DMISs (ie, public information services, professional services, science and education services, and e-commerce services). Business operation services mainly function to assist or facilitate the company’s operations and development trends for general visitors. Public-oriented information services are realized through health science popularization, academic frontiers, product information, and road maps to hospitals and pharmacies. Internet hospital and pharmacy services are the main patient-oriented professional services. Medical staff–oriented science and education services commonly include continuing education, clinical assistance, academic research, and journal searching. Public-oriented e-commerce services include health products and health insurance. Conclusions Pharmaceutical companies in China use WeChat to provide stakeholders with diversified DMISs, which remain in the exploratory stage. The service model of DMISs requires more distinct innovations to provide personalized digital health and patient-centric services. Moreover, specific regulations on the DMISs of pharmaceutical companies need to be established to guard public health interests.