It is well accepted that casualties incurred as a result of interstate militarized disputes have a significant influence on domestic public opinion and ultimately on foreign policy decision making (FPDM). Although scholars have studied the influence of casualties on FPDM, the major line of research ignores the possibility that different cultural settings may generate different levels of tolerance for human casualties and thereby differentially mediate public reactions. Therefore, I attempt to clarify the impact of cultural factors on interpretation and perception of human casualties in international conflicts by the general public and their implications on consequent foreign policy choices. I specifically examine two socio-cultural factors in the context of two culturally different states, South Korea and the United States. The two cultural factors are (1) the level of individualism vs. collectivism, and (2) the degree of ambiguity intolerance. I argue that the two factors will possibly affect the public’s tolerance of human casualties. I expect that they will affect both the process by which members of the two cultures make decisions and their choices. Cross-national experimental design (in South Korea and the United States) and a comparative case study were employed. Regarding the decision choice, I found that the expected number of casualties were considered in different ways by American students and Korean students. Different from my expectation, the Korean students perceived the expected number of casualties more negatively than the American students. With regard to the process of decision making, the empirical results support the hypotheses that the different levels of intolerance of ambiguity, a cultural factor, will have an impact on the decision process. Specifically, Korean students, who are less tolerant of ambiguity, needed less information to reach a final decision than did American students. Overall, although the results did not completely support cultural accounts, cultural explanation has been proven to be a viable ingredient in explaining the different observed patterns of foreign policy decision making. Specifically, a cultural factor, ambiguity intolerance, had an impact on the process rather than the choice. In addition, this study presents some theoretical implications as well as political implications.