Aims To explore Swedish adolescents' conceptual views of mental health and mental health problems. Design A qualitative descriptive study design. Methods Semi‐structured focus group interviews and individual interviews were conducted with, in total, 32 Swedish adolescents (15–18 years old) in October–November 2020. Data were analysed using systematic text condensation. Results Three themes were identified through the analysis: Mental health is about how we feel; One's mental health depends on one's situation, thoughts and ways of coping; and Mental health problems should be taken seriously and can get severe. Conclusion The results indicate that adolescents understand the complexity and holistic nature of mental health and mental health problems. According to the participating adolescents, positive mental health and mental health problems should be considered simultaneously to understand a young person's mental health state. Good health was described as having both absence of mental health problems and high levels of well‐being: feeling well. Mental health problems were defined as something other than normal difficulties in life, but ranging from minor difficulties to more severe conditions. However, all kinds of mental health problems were termed as feeling unwell. The results suggest that adolescents are in need of support to cope with normal difficulties in life rather than lectures about life sometimes being challenging. In addition, the results highlight the need to prevent school‐related stress and offer adolescents support for minor mental health problems. Impact The findings have implications for nurses and other professionals who encounter adolescents in their profession, for example specialist nurses, school nurses and public health professionals. The findings add knowledge that could be useful for communication with adolescents about their mental health and methods to assess their mental health status. Patient or Public Contribution The preliminary results were presented to three classes, in year nine in lower secondary school, for validation.