Different morphologies of NiO were synthesized by a simple hydrothermal method. The crystal structure, morphology, and specific surface area of synthesized NiO were characterized. Synthesized NiO particles were then electrophoretically deposited as a film for a sensing material. TEA-modification in the solution changed cube-like NiO particles to highly anisotropic needle-like particles during hydrothermal growth reaction. Electrophoretically deposited NiO sensing layer demonstrated improved sensing performance. Morphological feature with higher specific surface area appears to be important in gas sensing of NiO particles. (C) 2016 The Electrochemical Society.