Introduction An increased number of adolescents experience mental health problems. School nurses have described spending more than 50% of their time working with mental health in students. The lack of knowledge and necessary training to meet students’ mental health needs has been described previously. School nurses have a responsibility to find and guide those who need help with mental health problems. Objectives The aim of this study was, therefore, to explore school nurses’ experiences with mental health and how they in this work identify, talk, and intervene with adolescents having mental health problems. Methods A qualitative study was conducted with 21 school nurses using focus group interviews which were analyzed by means of content analysis. Results Three descriptive categories emerged: Health-promoting or preventive approaches, Enabling students to talk about feelings, and Collaborating partners. Conclusion School nurses highlight their mandate to work with health promotion and prevention but also draw attention to their difficulties in identifying those who need help. School nurses use their creativity, intuition, and knowledge but have difficulty identifying those students who need help with mental health problems. They also highlight collaboration with other professionals both in schools and in the health system.