PURPOSE: Exposure to breastfeeding improves the survival, health, and development of children; therefore, breast milk is recommended as the exclusive nutrient source for feeding term infants during the first 6 months. This cross-sectional study aimed to determine the possible association between exposure to exclusive breastfeeding and physical fitness performance in children and, if so, whether this association is influenced by the breastfeeding duration. METHODS: A total of 2853 (52.3 % girls) European children from the IDEFICS study aged 6-11 years with complete data on physical fitness (cardiorespiratory fitness, muscular strength, flexibility, balance, speed) and exclusive breastfeeding duration (never, 1-3, 4-6, 7-12 months) were included in the present study. Multivariate and mixed linear regression models were estimated and adjusted for sex, age, birth weight, diet, physical activity, body mass index, and parental factors (age, body mass index, educational attainment). RESULTS: We found a positive association between exclusive breastfeeding and lower-body explosive strength (β = 0.034) as well as flexibility (β = 0.028). We also found a positive association between breastfeeding and balance in boys (β = 0.039), while this association was negative in girls (β = -0.029). To improve lower-body explosive strength, 1-3 months of exclusive breastfeeding were enough; a longer duration did not lead to increasing benefit. In contrast, 4-6 months of breastfeeding were necessary to have any benefit on flexibility or balance, although this became nonsignificant after adjustment for body mass index and physical activity. CONCLUSIONS: Exclusive breastfeeding seems a natural way of slightly improving some physical fitness components (mainly lower-body muscle strength) and thus future health.