Spherical V₂O₅ hierarchical structures made up of nanosheets have been synthesized via a facile hydrothermal method without any surfactants and a following annealing process in air. The structure, chemical compositions and morphological features of the V₂O₅ sample have been investigated through XRD, XPS, SEM and TEM. Besides, the optical properties and the growth period are also investigated. Sensors based on spherical V₂O₅ hierarchical structures exhibit good selectivity to trimethylamine (TMA), fast response/recovery times (5/28 s), and good stability and repeatability at an operation temperature of 240 °C with a gas concentration of 100 ppm. All these properties are related to the unique 3D spherical hierarchical structures. Finally, a gas sensing mechanism based on the chemisorption process is proposed.