The tongue has a wide variety of motor functions, which are driven by tongue muscle contractions and associated with movements of the hyoid bone (HB) connected to the tongue root. HB movement has been observed in many situations, including swallowing, breathing, and speech. However, the relationships between HB movement and tongue kinematic function have received little attention, and have not been considered in most previous biomechanical tongue modeling research, except studies of swallowing. The current study aimed to clarify the effects of HB movement on tongue kinematics during tongue forward protrusion, which is an essential tongue motor function associated with speech disorder. HB displacement during tongue forward protrusion was quantified using ultrasound imaging in four healthy controls. Furthermore, computational mechanical simulations of tongue forward protrusion were conducted with observed HB movements and active contraction of the genioglossus (GG) muscle, which is conventionally considered to be the driving muscle in tongue forward protrusion. Ultrasound imaging revealed anterosuperior HB displacement in tongue forward protrusion, with a similar magnitude in each direction (anterior:​ 6.3 ± 2.8 mm, superior:​ 5.8 ± 1.6 mm). Computational simulation demonstrated that the HB movement described above caused not only anterosuperior displacement, but also forward rotation of the tongue body, which was caused by kinematic constraints of GG. The resulting anterior displacement of the tongue tip was 1.5 times greater compared with that without HB movement. These findings indicate that the HB and associated tongue body movements play non-negligible roles in the tongue kinematics of forward protrusion.