Research that focuses on the relationship between interpersonal conflict at work (i.e., intragroup conflict and intergroup conflict) and depression that also considers differences in socioeconomic status (SES) is limited. The purpose of the current study is to investigate the relationship between interpersonal conflict at work and depression at different levels of SES. A cross-sectional study was conducted with a total of 17,390 males and 2923 females employed in nine factories located in several regions of Japan. These participants were surveyed using a self-administered questionnaire that included self-reported measures of interpersonal conflict at work (intragroup conflict and intergroup conflict), SES (education and occupation), worksite support (supervisor support and coworker support), depression (assessed using the Center for Epidemiologic Studies Depression [CES-D] scale), and other demographic covariates. Those who had scores of 16 + on the CES-D scale (4066 males and 873 females) were classified as experiencing depression. The association of interpersonal conflict with depression was significantly greater among males of a high SES (i.e., higher educational status and non-manual workers) than males of a low SES (i.e., lower educational status and manual workers) after adjusting for demographic variables, supervisor support, and coworker support. More specifically, the association of intergroup conflict with depression was significantly greater among males of a high SES than males of a low SES. However, this pattern was not observed in females. The current study suggests that males of a higher SES are more vulnerable to interpersonal conflict at work in terms of developing depression than males of a lower SES. © 2010 Elsevier Ltd.