Introduction: The mouthguard is mainly used as a preventive measure to protect teeth from traumatic events. Effects on posture have not been sufficiently analyzed so far. Therefore, this study evaluates the influences of mouthguards on functional posture during movements in field hockey players. We compared a control condition (wearing no mouthguard) with two experimental conditions (wearing a common mouthguard and wearing an individually-fittedmouth guard). Methods: Functional posture of the spinal column was measured in these three conditions. Twelve field hockey players of a First National League team participated in this study. Measurement device was the sonoSens®Monitor which is based on a continuous ultrasonic system. Results: Functional differences were observed while wearing a mouthguard during flexion, extension, lateralflexion and torsion mainly in thoracic spine. This can be seen in standing and walking as well as during hockey-specific movements. The mouthguard leads to erection and derotation of the body posture compared to the control condition. Discussion: The mouthguard has not only a protective function, it seems to be able to influence the functional posture of the spinal column of field hockey players, when it is individually fitted in centric jaw relation.