A series of nanostructred La1−xCexCoO3 perovskite-type (x ranging from 0 to 0.2), with a crystallite size of around 10nm and a specific surface area of up to 55m2/g were prepared using the activated reactive grinding method. XRD results showed that Ce segregates as CeO2 when the addition level exceeds 10at%. CO was chosen as a typical reducing gas and its interaction with surface oxygen was investigated. TPD-O2 was used to investigate the effect of Ce-doping on total surface oxygen. The experimental results confirmed a positive effect of Ce-doping of up to 10at% on total surface oxygen (α-O2). TPD-CO and XPS analyses were performed to find the total carbon adsorption (i.e. related to the adsorption of CO) on the surface of the synthesized samples. Both methods confirmed that more carbon adsorbs on the surface of doped formulations compared to the pure LaCoO3. Ce-doping increases the surface oxygen, thereby facilitating the adsorption and oxidation processes. CO gas sensing properties of thick La1−xCexCoO3 films were performed. La0.9Ce0.1CoO3 showed the highest conductivity and the lowest activation energy. The optimum CO sensing temperature for doped formulation was found to be 100°C compared to 130°C for pure perovskite. Ce-doped samples showed a maximum response ratio of 240% with respect to 100ppm CO in air compared to 60% obtained with pure LaCoO3.