Background: The aim of this paper is to illustrate the expansion of mandibular arch using Transforce appliance. Case Report: Use of Transforce appliance for arch expansion for severely constricted mandibular arch. The patient is successfully treated with arch expansion. Conclusion: Transforce appliance is a good choice for mandibular arch expansion. Since mandible lacks sutures to open up, light force is required for arch development and Transforce appliance is capable of producing light forces.