The concept of health contains aspects of social and mental well-being and not just the absence of disease. The concept of well-being is sometimes used interchangeably with the term happiness, although focus has been on other aspects as well. Here we explore associations between happiness and experience of stress at school, personal and social factors among 887 Norwegian school adolescents participating in a World Health Organization project on health-promoting schools. Happiness was measured by a one item question (ordered responses 1–4). The psychosocial factors were represented by an average score of 3–12 items. Odds ratios of feeling very/quite happy were calculated in multiple logistic regression analyses. An increasing degree of stress experience reduced the feeling of happiness significantly. Furthermore, increasing levels of general self-efficacy increased the odds of feeling happy, whereas the more specific measure of school self-efficacy showed no independent effect. Social support from teachers also enhanced happiness significantly. A less consistent pattern was found for support from peers, but the most happy pupils experienced significantly more support than pupils who reported being unhappy. No significant trend was found with decision control. We also explored associations between happiness and psychosomatic symptoms. Pupils feeling unhappy reported a particular symptom more often and they also had the highest mean number of reported symptoms. To evaluate whether these health indicators represent different dimensions of health, a comparison of strength of associations with common risk factors is made. Implications for health promotion practice are discussed.