The purpose of this study is to verify the moderating effect of social support in the relationship between maladaptive perfectionism and career decision-making self-efficacy. For this purpose, this study confirmed moderating effect by setting maladaptive perfectionism as predicting variable, social support as moderating variable and career decision-making self-efficacy as dependent variable. The study conducted a questionnaire survey on 322 university students regarding maladaptive perfectionism, social support and career decision-making self-efficacy. The results of this study are as follows; first, maladaptive perfectionism had negative correlation with social support and career decision-making self-efficacy while social support had positive correlation with and career decision-making self-efficacy. Second, as the result of hierarchical regression analysis, there was an interaction effect of maladaptive perfectionism and social support on career decision-making self-efficacy. That is, it turned out that social support moderated the relationship between maladaptive perfectionism and career decision-making self-efficacy. Based on these study results, this study discussed meaning, implications and limitations of the study and suggestions for follow-up studies.