Objective To investigate the effect of splint therapy on masseter muscle and blood flow in patients with bruxism using ultrasonography (USG). Methods Twenty female patients with bruxism receiving splint treatment were studied. Masseter thickness and elasticity were assessed using gray-scale USG and shear-wave elastography (kPa) at rest and maximum clenching. Blood flow parameters of external carotid artery (ECA), maxillary, facial, mental artery were examined using Doppler USG before and after splint application. Results Thickness and elasticity of masseter muscle was statistically significantly decreased at rest after splint therapy (p < 0.05). Significant difference was determined only in some parameters of ECA and maxillary artery in Doppler USG before and after splint (p < 0.05); there was no difference for facial and mental artery (p > 0.05). Conclusion Thickness and elasticity of masseter muscle were significantly decreased after splint therapy. USG can measure muscle activity and blood flow in bruxism patients.