A comparative study of ionic conductivity in a series of alkali metal nitrites was carried out. Experimental results were interpreted in terms of the classical model of Schottky defect formation in ionic crystals when the cationic vacancies are the dominating charge carriers. The point defect formation and migration parameters were evaluated by fitting of the theoretical model to the experimental data. It was demonstrated that in a series of alkali nitrites both the defect formation and the migration enthalpies decrease with the cationic radius leading to the increase in the conductivity as a function of the cationic size. As a result, the cesium nitrite has the highest conductivity among alkali nitrites.