•Facile method has employed to prepare mesoporous Co3O4 nanochains with high specific surface area.•The Co3O4 nanochains has highly sensitive and selective toward H2S gas with rapid response.•Such a potential gas sensing strategy can be easily extended to other metal oxides. In this paper, cobalt carbonate hydroxide (Co(CO3)0.5(OH)..11H2O) nanowires were successfully fabricated by a simple hydrothermal route without using surfactants and by subsequent heat treatment in air at 600 °C for 5 h to obtain mesoporous Co3O4 nanochains. As-synthesized nanochains with length of several micrometers consisted of well-linked Co3O4 nanoparticles with an average size of 50 nm. The sensor based on mesoporous Co3O4 nanochains was used to detect flammable and toxic gases, including H2S, NH3, CO, and H2. Results showed potential of mesoporous Co3O4 nanochains as sensor material for detection of hydrogen sulfides at low concentration with rapid response.