Purpose This study aims to evaluate the efficiency of low-level laser therapy vs injection of long acting anesthetic drug as an adjunctive treatment in combination with muscle relaxant splint in treating patients suffering from myofascial pain dysfunction syndrome (MPDS). Patients and methods A total of 36 MPDS female patients represented the candidates of the present study. They were all treated with muscle relaxant splint then randomly divided into three equal groups; group 1 was treated solely with occlusal splints; group 2 was treated with long acting anesthetic injection of both the masseter and temporalis muscles bilaterally in combination with the splint therapy, while group 3 was treated with low-level laser therapy in combination with the splint therapy. Results All patients completed the study period with improvement in their visual analog scale, mouth opening and electromyography. Group 3 showed statistical significant improvement in all measures compared to group 1 and group 2. Conclusion All the utilized treatment modalities aided in reliving the signs and symptoms of the MPD patients and improved their mouth opening and muscle activity. Utilizing low-level laser therapy in combination with splint therapy was found to be the best adjunctive treatment modality, compared to the injection of long acting anesthetic agent and splint therapy.