Today in the United States, outbreaks of vaccine-preventable disease are often traced to susceptible children whose parents have claimed an exemption from school or child care immunization regulations. The origins of this immunization hesitancy and resistance have roots in the decline of the threat of vaccine-preventable disease coupled with an increase in concerns about the adverse effects of vaccines, the emergence of mass media and the Internet, and the intrinsic limitations of modern medicine. Appeals to emotion have drowned out thoughtful discussion in public forums, and overall, public trust in immunizations has declined. We present an often overlooked behavior change strategy-social marketing-as a way to improve immunization rates by addressing the important roots of immunization hesitancy and effectively engaging emotions. As an example, we provide a synopsis of a social marketing campaign that is currently in development in Washington state and that is aimed at increasing timely immunizations in children from birth to age 24 months.