The diverse benefits that a sense of humor provides to individuals and organizations have long been recognized by many people. Specifically, the health benefits of a sense of humor, the psychological benefits of being able to cope well with difficult environments, the interpersonal benefits of facilitating smooth interpersonal relationships and enhancing intimacy through the appropriate use of humor, and the cognitive benefits of helping people break out of existing frameworks to promote new ideas have all been discussed. Recently, as several management scholars and corporate leaders have recognized that a sense of humor is an important element in strategic management, studies on the effects of a sense of humor on business performance have been conducted. However, most of these studies have, first, focused only on the relationship between sense of humor and creativity performance, while research on what effects a sense of humor has on various other forms of organizational performance remains insufficient. Second, although various mediating variables such as self-efficacy, sociability, and self-esteem can be considered between sense of humor and organizational performance, research on these variables is virtually nonexistent. Third, domestic research on humor has primarily been conducted broadly in the fields of nursing, psychology, education, and advertising as studies on stress coping or intervention, while research directly using sense of humor and job attitudes as independent and dependent variables is rare, and research in the management field in particular is difficult to find. In this context, the purpose of this study is to analyze the effects of a sense of humor on organizational performance and to verify whether self-efficacy plays a mediating role between the two. To achieve this purpose, this study limited the surveyed firms to domestic companies, but selected a total of 20 companies across Korea appropriately reflecting variables such as manufacturing versus non-manufacturing and large versus small-to-medium enterprises, distributing an average of 20 questionnaires per company for a total of 400 questionnaires. Survey respondents were limited to managers at the assistant manager level and above, regardless of region or department, since career performance—one of the dependent variables used in this study—requires a certain degree of work experience. Using 181 valid responses for analysis, the results showed that a sense of humor not only had a positive effect on organizational performance—namely job performance, career performance, creativity performance, and team performance—but also that self-efficacy mediated the positive relationship between sense of humor and organizational performance (job performance, career performance, creativity performance, and team performance). The theoretical and practical implications of this study's results are as follows: First, by demonstrating that a sense of humor has positive effects on various forms of organizational performance, this study contributed to extending existing research findings on sense of humor in both theoretical and empirical dimensions. Second, this study revealed that Korean organizations should also actively utilize humor and make efforts to develop and enhance employees' sense of humor for the improvement of organizational performance. Third, this study presented a theoretical framework for the mediating effect of self-efficacy on the relationship between individual sense of humor and organizational performance and empirically tested it.