Multimorbidity, that is, the coexistence of chronic diseases, is associated with mental health issues among elderly people. In Sweden, seniors with multimorbidity often live at home and receive care from nursing aides and district nurses. The aim of this study was to describe the variation in how community-dwelling seniors with multimorbidity perceive the concept of mental health and what may influence it. Thirteen semi-structured interviews were analysed using a phenomenographic approach. Six qualitatively different ways of understanding the concept of mental health and factors that may influence it, reflecting key variations of meaning, were identified. The discerned categories were: mental health is dependent on desirable feelings and social contacts, mental health is dependent on undesirable feelings and social isolation, mental health is dependent on power of the mind and ability to control thoughts, mental health is dependent on powerlessness of the mind and inability to control thoughts, mental health is dependent on active behaviour and a healthy lifestyle, and mental health is dependent on passive behaviour and physical inactivity. According to the respondents' view, the concept of mental health can be defined as how an individual feels, thinks, and acts and also includes a positive as well as a negative aspect. Social contacts, physical activity, and optimism may improve mental health while social isolation, ageing, and chronic pain may worsen it. Findings highlight the importance of individually definitions of mental health and that community-dwelling seniors with multimorbidity may describe how multiple chronic conditions can affect their life situation. It is essential to organize the health care system to provide individual health promotion dialogues, and future research should address the prerequisites for conducting mental health promotion dialogues.