Previous researchers have found that low body satisfaction may be a barrier to engaging in physical activity. Therefore, this research examines the association between self-concept, body dissatisfaction, fitness, and weight status in adolescents. The sample was formed by 303 students from primary schools, (males (n = 150) and female (n = 153)) aged 10 to 13 years (M = 11.74; SD = 0.86). Initially, participants’ BMIs, as well as waist-to-hip ratio were assessed. Later, all individuals answered a questionnaire about their perception of self-concept and body image perception. Moreover, agility run test and 6-min walking test were developed to assess children’s physical fitness. Results showed self-concept differences according to different fitness level. Moreover, some factors from self-concept emerged as relevant to explain body dissatisfaction. Finally, outcomes suggest the importance of physical fitness and the perception of competence and self-esteem in adolescent boys and girls, so these two issues might be promoted in primary school classes to improve body satisfaction.