The aim of the present study is to demonstrate the empirical distinctiveness of workaholism and work engagement by examining their relationships with well-being in a sample of 776 Japanese employees. We expected that workaholism is associated with unwell-being (i.e., high psychological distress and physical complaints, low job and family satisfaction, and low job performance), whereas work engagement is associated with well-being. Well-validated questionnaires were used to measure workaholism (DUWAS), work engagement (UWES), and well-being (BJSQ, HPQ). Structural Equation Modeling showed that, as expected, workaholism was positively associated with ill-health (i.e., psychological distress and physical complaints) and negatively associated with life satisfaction (i.e., job and family satisfaction) and job performance. In contrast, work engagement was negatively associated with ill-health and positively associated with life satisfaction and job performance. These findings suggest that workaholism and work engagement are two different kinds of concepts, which are negatively and positively related to various indicators of well-being, respectively.