The purpose was to investigate stress among adolescents (16–19 years old) during the coronavirus disease 2019 (COVID-19) pandemic. Focus group (n = 9) interviews with students at upper secondary schools (16–19 years old, n = 41) were conducted in southern Sweden during the COVID-19 pandemic in 2021. The interviews were analyzed by qualitative content analysis. The analysis revealed five categories of experience of stress: (1) School-related stress, (2) Stress in relationships and leisure, (3) How stress manifests itself, (4) Stress can increase performance, and (5) Experiences of counteracting stress. The adolescents in the study experienced stress linked to school and relationships, partly due to the COVID-19 pandemic. Distance education during the COVID-19 pandemic increased stress levels. The adolescents stated that high stress levels were experienced negatively and impaired their ability to perform, while moderate stress could contribute to achieving goals and improving performance. School nurses and other health professionals who meet with adolescents are important to support adolescents experiencing stress.