The status of adolescents' mental health has detoriorated in the last 20 years. Socio-economic factors contribute to the health status of adolescents. The aim of the study was to explore the relationship between socio-economic factors and self-rated mental health and the hypothesis tested was that household wealth influences the association. The study was based on the Halmstad Youth Quality of Life (QoL) 2012, collected at junior high schools in the town Halmstad in Sweden. Logistic regression models were used to test the associations between socio-economic factors and the risk of scoring low mental health. This study found differences between girls and boys where girls rated their mental health lower. Among adolescents 11-13 years old, no association was seen between socio-economic factors and mental health. In the older age group, both girls and boys suffered an increased risk of low mental health when parents were divorced or separated, however, when adjusting for household wealth, the relationship disappeared. Among boys 14-16 years old, the risk of low rated mental health was affected by having parents born outside Sweden and having an increased number of socio-economic risk-factors clustered, and this was independent of household wealth. No such trend was seen among older girls. Our hypothesis that household wealth had a major association with adolescents' rating of their mental health was not obvious.