Body dissatisfaction is a phenomenon that may already occur in childhood and is linked to a variety of psychosocial risks. As the role of physical activity in the context of body dissatisfaction is still ambivalent, a cross-sectional study with 602 normal weight children (50.2% girls; M = 9.23 years; SD = 0.79) was conducted. The children filled in the MoMo-Questionnaire, including items about their physical activities and motives for being physically active, as well as Bender's Body Esteem and Muscularity Concern Scale with the three subscales "body satisfaction", "weight and shape concerns", and "muscularity concerns". Independent t-tests revealed that girls were less worried about muscularity than boys (M= 1.94, SD= 1.11 vs. M= 3.12, SD= 1.43; t(560) = 11.33, p < .001, Cohen's d = 0.92), whereas girls showed greater weight and shape concerns than boys (M= 2.24, SD= 0.97 vs. M= 2.05, SD= 0.92; t(549) = 2.32, p = .02, d = 0.20). In boys, physical activity is associated with less muscularity, weight, and shape concerns. Body satisfaction increases with health and fitness motives. In girls, the role of physical activity is ambivalent: girls who engage in sports do not differ in body dissatisfaction from non-active girls. In sportive girls, weight and shape concerns increased with more health and fitness motives. Finally, the study provides first insights into body dissatisfaction and the different role of physical activity in boys and girls in childhood.