The objective of this study was to illustrate the relationship between optimism and defense mechanism in Korean college students. 332 student participants from “A” University in Korea completed questionnaires from the Ewah defense mechanism and optimism measurement tool. This study analyzed the culled data and revealed general patterns of optimism and defense mechanism, as well as patterns based on gender. In addition, the study analyzed differences in defense mechanism, dictated by one’s optimism level. Frequency, percentage, mean, standard deviation, and t-test were analyzed using SPSS 21.0. The results demonstrated that the operating defense mechanism in Korean college students were different for males and females in the categories of show-off, passive aggressive, denial, and identification. However, the level of optimism was identical for both genders. Defensive mechanisms based on optimism levels also varied significantly in controlling, distortion, altruism, humor, sublimation, and rationalization categories.