Lithiated nickel oxide is currently used as the molten carbonate fuel cell cathode. The lithium concentration in NiO is very low but no quantitative determination is available. However, the presence of lithium is a key factor for NiO conductivity, but this species is difficult to detect in low amounts. Therefore, the nuclear microprobe technique was used, for the first time, to measure lithium concentration and its depth profile in the NiO cathode. The lithium amount varies between 0.1 and 0.5 atom %, according to the melt exposure duration and the analyzed position in the layer thickness.