Over the past 50 years, tobacco control has been transformed from a national to a global issue, becoming institutionalized in the World Health Organization (WHO) Framework Convention on Tobacco Control, the first international public health treaty negotiated under the auspices of the WHO. The global tobacco control epistemic community, a worldwide network of professionals with a common interpretation of the science in tobacco use and control, has contributed to this transformation. We investigated the development, structure, and function of this community through interviews and archival documents. Professionals in the community are bound by values and consensual knowledge developed after years of contentious debates undergirded their activities. Although these professionals play multiple roles, they recognize that scientific evidence should inform advocacy and policy activities. Public health professionals should continue to strengthen the links between science and advocacy for policy while being vigilant against industry efforts to undermine the scientific evidence on tobacco use and control.