This longitudinal study investigates how the introduction of mandatory pictorial health warnings regulation in 2016 changes South Korean smokers’ cognition, affection and conation. 246 smokers participated in this study and their attitudes toward graphic health warnings and smoking cessation behavior changes were analyzed following five stages in the message impact framework descriptively. The results find that the introduction of graphic health warnings was effective to increase smokers’ attention and deliberation to the warning messages. However, the graphic health warnings also increased negative emotions and, thus, made smokers to avoid the warning messages. In conclusion, the introduction of graphic health warnings was effective to induce emotional responses which make smokers to subjectively realize threats from smoking but ineffective to change their prior beliefs and knowledge regards smoking. Introduction of the graphic health warnings encouraged smokers’ cessation trials especially those who had a willingness to stop smoking. This study contributes to marketing communication as well as public policy research in a way to test the differences before and after introducing a new regulation that required the graphic health warning labels displayed on tobacco products sold in South Korea.