Over the past decade mental health problems among adolescents in Sweden has increased. Psychosomatic symptoms and stress accounts for a large proportion of the disease burden. Social capital is a social resource that can strengthen the individual’s well-being. The aim of the study is to examine if social capital is related to psychosomatic symptoms and stress, as well as if there are gender differences in social capital, psychosomatic symptoms and stress among adolescents. A quantitative method was chosen, and the study used secondary data from Survey of Adolescent Life in Västmanland 2012, which had a cross-sectional design. Statistical analyses were carried out to answer the aim of the study. There was 87% of the adolescents that reported high levels of social capital, whereas 72% reported high levels of psychosomatic symptoms and 65% felt stressed. There was a statistically significant negative relationship between social capital and psychosomatic symptoms, also a relationship between social capital and stress. Boys reported higher levels of social capital than girls. Girls reported higher levels of psychosomatic symptoms and felt stressed compared to boys. The results were consistent with previous research regarding psychosomatic symptoms and stress, where girls were affected to a greater extent than boys.