We report a first principles study on the electronic structure of CdSe nanosheet under strain. Our results suggest that the band structure of CdSe nanosheet experiences a transition from being semiconducting to metallic with increased symmetrical strain. Such transition is not found under asymmetrical (along zigzag or armchair direction) strain. Moreover, the band gap of CdSe nanosheet responds differently among symmetrical, zigzag and armchair strain. A detailed discussion on the strain dependence effect is also presented via the electron localization function, the charge transfer between Cd and Se atoms, and the evolution of energy states at C and K point. (C) 2014 Elsevier B.V. All rights reserved.