Purpose: To assess the electromyographic activity of oral muscles concomitant to Class II malocclusion correction using Carrier Distalizer appliance. Materials and Methods: 10 female patients with age ranged between (18-21) years old were selected for this study. All patients were examined to fulfill the inclusion criteria. All patients in this study underwent radiographic evaluation (panoramic and lateral cephalometric) and electromyographic evaluation before and after Class II correction using Carrier Distalizer appliance. Study duration for patients was six months. Results: The result of this study showed that no significant changes occurred in skeletal measurements except increase angle of convexity. Regarding electromyographic measurements there is statistically significant increase in masseter muscle activity at rest and at occlusion after treatment. And about the dentoalveolar changes including slight maxillary molar distalization, in addition to mesialization of the lower molars and proclination of the lower incisors. Conclusion: It was concluded that Carrière Distalizer appliance was able to correct Class II molar relation into Class I relation in adult patients with masseter and temporalis muscles activity were improved after treatment.