The aim of this study was to see the effect of twin block appliance in permanent dentition phase. Twin block from its inception and evolution of the appliance itself has been widely accepted as a more competent Class II corrector compared to earlier bulky monopoly appliances. The effect of the twin block functional appliances is mostly dent alveolar having a small skeletal effect. Functional appliances can be used successfully in growing patient with certain Class II malocclusion. It is dependent on patient’s compliance. It also simplifies the fixed appliance phase. A 13-year-old girl was treated with twin block appliance. The design of appliance and treatment results were demonstrated in following case report. In permanent dentition, twin block appliance produces a similar effect as in mixed dentition phase. With proper case selection and good patient cooperation, we can obtain a significant result with twin block appliance.