Co-occurring mental illness and addiction – a unity that forms everyday life People with co-occurring mental illness and addiction tend to be a vulnerable group in society, often in need of extensive and collaborative care. From a social work perspective, it is crucial to gain more knowledge about these persons’ everyday lives and living conditions. The aim of this article is to explore how people with co-occurring mental illness and addiction experience their everyday lives and develop knowledge about how everyday life is structured by these co-occurring illnesses. Using a narrative method, 12 persons were interviewed, sharing their experiences. The analysis was performed using the theory of the everyday life, the normative and structural aspect. The findings suggest that participants’ understanding of the co-occurring mental illness and addiction is described as a continuous interaction between the two illnesses and experienced as a unity. The narratives imply that dysfunctional family relationships in everyday life during childhood, losing employment and financial problems are shared experiences. The narratives also include loss of everyday routines due to co-occurring illnesses, unemployment and homelessness. Therefore, several routines, such as sleep, food and household routines are negatively affected. The conclusion is that the persons’ everyday life experiences starting as early as childhood have consequences for how their adulthood is structured, where the co-occurring mental illness and addiction play a central role in everyday life, affecting various aspects of it. The implications for practice are to view and treat the co-occurring illnesses as the persons understand them, namely as a unity that affects several everyday life arenas, and offer help to create and maintain routines, economic support and participation in activities.