Objective: To evaluate and compare the treatment changes with Twin block appliance in class II division 1 malocclusion patients. Materials and methods: Twenty subjects with Class II division 1 malocclusion were chosen. The subjects were treated with Twin block appliance (n = 20; mean age: 11.2yrs). Pre–functional and post–functional cephalograms were traced and subjected to analysis. Results: Skeletal effects seen as increase in mandibular length were significant. Overjet correction with Twin block occurred mainly as a result of mandibular repositioning and growth. Differential eruption of mandibular molars was observed. Changes in lip position improved the overall profile. Conclusions: Twin block is effective in correcting Class II malocclusion, however Twin block causes more skeletal changes than dentoalveolar.