Objective To examine how video messages from a recent media campaign affected public attitudes about obesity prevention and weight-based stigma toward obese children. Design and Methods A survey-embedded experiment in May-June 2012 with nationally representative sample (N = 1,677) was conducted. Participants were randomized to view one of three messages of children recounting struggles with obesity, or to a control group. It was examined whether message exposure affected attitudes about: 1) the seriousness of childhood obesity and its consequences; 2) responsibility for addressing obesity; 3) support for prevention policies, and 4) stigma toward obese children. Results Participants viewing the messages attributed greater responsibility for addressing childhood obesity to the food and beverage industry, schools, and the government, compared to those in the control group. Overweight and female respondents viewing the messages reported lower weight-based stigma compared with overweight and female respondents in the control group, but messages had no effect on healthy weight and male respondents. Messages did not affect attitudes about the seriousness of childhood obesity, its consequences, or support for obesity prevention policies. Conclusions It will be critical to assess on an ongoing basis how communication campaigns addressing childhood obesity shape public attitudes about obesity prevention.