The purpose of this study was to analyze the post-purchase behavior of customers who experienced cognitive dissonance after exposure to a franchise foodservice advertisement. The study adopted cognitive dissonance theory to explain the dissonance resulting from the combination of advertisements and actual product that consumers received. In detail, the research hypothesized that cognitive dissonance will affect consumers’ post-purchase behavior as well as their efforts to reduce dissonance. Exactly 274 questionnaires were used in the analysis. The results showed that more than 80% of respondents were influenced by advertisements when purchasing menus, and 50% were unsatisfied when the provided menu “was not the same as the advertisement shown.” It was found that advertisement type did not significantly affect either group that experienced dissonance. In terms of satisfaction, however, the former group showed greater dissatisfaction when dissonance occurred (p<.001). Finally, there was a significant difference between the two groups regarding post-purchase behavior (p<.05). Customers with dissonance were likely to ‘express dissatisfaction directly to the store’, ‘leave negative reviews’, and ‘participate in negative word-of-mouth’. Thus, the results revealed that cognitive dissonance could significantly influence customer satisfaction and consequently lead to negative post-purchasing behaviors.