Managing people from different backgrounds has brought great benefits to work organizations. However, previous research has shown that diversity may have negative effects on performance because of diversity “faultlines”, hypothetical dividing lines that may split a group into subgroups. We conducted an empirical study on faultlines for the first time in Japan to investigate the present status of faultlines and to assess the degree to which workers perceive that (certain) attributes (e.g. nationality, ethnicity, age, personality, attitude) may have an impact on the emergence of faultlines in Japanese work organizations. It has been shown that task-related attributes such as specialty and ability/knowledge are great factors affecting faultlines, and that every participant perceives faultlines based on such attributes as specialty, personality, and attitude.