In this study, undoped and Cobalt-doped Al 2 O 3 were synthesized though a precipitation method followed by microwave irradiation for benzene gas sensing studies. The Co-doped Al 2 O 3 nanoparticles are offering lattice disorder that facilitate imperfection/defects. An XPS survey scan has been used to confirm the presence of the relevant elements and to calculate their amounts, respectively. Moreover, the doped nanoparticles face shape and size revision which warrants the device application. After characterization, the samples were used for fabrication of gas sensors. Benzene gas sensing studies revealed that the sensor with higher amount of Co-doping had a high response to this gas. The optimized gas sensor showed a fast response time of 1.5 s and a recovery time of 2 s. The doped sensor has effectively sensed the lower concentration of 5 ppm gas. Sensor surface is readily active for grabbing oxygen from air and then release electrons at very fast in-contact of benzene. Furthermore, it showed high stability and good selectivity. Improved performance for the optimized gas sensor was related to decrease of particle size as a result of doping, generation of oxygen vacancies due to the presence of Codopant and also catalytic activity of Co. The ageing-test of the sensor had reproduced the ∼ 98 % results which affirms the long-term stability. The result of this study can be used for further exploration of role of Co in the gas response of different sensing materials.