A longitudinal survey study was conducted to examine which strategies for reducing cognitive dissonance were used among men engaging in infidelity. Data were collected in two waves, 1 month apart ( n time1 = 1514, n time2 = 425), from a sample of male users of Ashley Madison, a “married dating” site targeting users who are seeking to engage in infidelity. Because perpetrators of infidelity may justify their behaviors differently depending on whether they cheated in an online environment, both online and offline infidelity behaviors were considered. Results indicated that attitude change and self-concept change were positively related to online infidelity, while only self-concept change was positively related to offline infidelity, suggesting their differential effectiveness for various communication media. Self-concept change, attitude change, and denial of responsibility were negatively related to psychological discomfort and perceived negative impact at time 2, indicating their relative success for reducing negative psychological outcomes compared to other strategies such as adding consonant cognitions.