Background: The purpose of this study was to analyze the relationship between body posture and sagittal dental overjet in children before and after early orthodontic treatment with removable functional orthodontic appliances. Methods: Angle Class II patients (mean age 8.2 ± 1.2 years; 29 males and 25 females) with a distinctly enlarged overjet (> 9 mm) were retrospectively examined regarding body posture parameters before and after early orthodontic treatment. In addition, changes in overjet were investigated with the aid of plaster models. Forms of transverse dysgnathism (crossbite, lateral malocclusions) and open bite cases were excluded. Body posture parameters kyphosis, lordosis, surface rotation, pelvic tilt, pelvic torsion and trunk imbalance were analyzed by means of rasterstereographical photogrammetry to determine, if the orthodontic overjet correction is associated with specific changes in posture patterns. Results: In nearly all patients an overjet correction and an improvement regarding all body posture and back parameters could be noted after early orthodontic treatment. Overjet reduction (− 3.9 mm ± 2.1 mm) and pelvic torsion (− 1.28° ± 0,44°) were significantly (p  0.05). Conclusion: Overjet reduction during early orthodontic treatment may be associated with a detectable effect on pelvic torsion.