Perceived health is an important health predictor, and self-assessed health during adolescence is of great interest. This study examined the relationship between perceived negative health and body image in early and mid-adolescence, focusing on age and gender differences. Analyses were based on Norwegian data from a World Health Organization cross-national survey (Health Behaviour in School-Aged Children) among 5026 pupils aged 11, 13 and 15 years. The response rate was 76%. Stratified analyses with presentations of frequency and relative risk were performed, as well as logistic regression analyses. Girls are more likely to report negative health than boys are, and the probability of such reports increases with age. Girls and older age groups report dieting and dissatisfaction with weight and appearance more often than boys and younger age groups. Body dissatisfaction is associated with an increased risk of perceived negative health, also when controlling for the possible confounding effects of age and gender. The present 'ideals' of weight and appearance might contribute to an unfavourable perception of health in this age group.