Antismoking mass media campaigns are known to be effective as part of comprehensive tobacco control programs in high-income countries, but such campaigns are relatively new in low- and middle-income countries and there is a need for strong evaluation studies from these regions. This study examines Malaysia's first national antismoking campaign, TAK NAK. The data are from the International Tobacco Control Malaysia Survey, which is an ongoing cohort survey of a nationally representative sample of adult smokers (18 years and older; N = 2,006). The outcome variable was quit intentions of adult smokers, and the authors assessed the extent to which quit intentions may have been strengthened by exposure to the antismoking campaign. The authors also tested whether the impact of the campaign on quit intentions was related to cognitive mechanisms (increasing thoughts about the harm of smoking), affective mechanisms (increasing fear from the campaign), and perceived social norms (increasing perceived social disapproval about smoking). Mediational regression analyses revealed that thoughts about the harm of smoking, fear arousal, and social norms against smoking mediated the relation between TAK NAK impact and quit intentions. Effective campaigns should prompt smokers to engage in both cognitive and affective processes and encourage consideration of social norms about smoking in their society.