The stability of aqueous suspensions of α-chitin nanocrystals under various storage conditions is studied. Suspensions obtained by TEMPO oxidation, in which owing to the modification of hydroxyl groups C6 on the surface of nanoparticles negatively charged carboxyl groups are formed, stabilizing chitin suspensions in an alkaline aqueous medium. To study changes occurring in α-chitin nanocrystals, two series of suspension samples are prepared: samples containing sodium azide as a biocide and control samples without it. Changes in the suspension of the samples kept at room temperature and +4°C for 16 weeks are monitored by IR spectroscopy, atomic force microscopy, and dynamic light scattering. It is shown that the size of individual nanocrystals does not change during storage. In this case, an additional peak with a small hydrodynamic radius appears on dynamic light scattering curves, which is apparently associated with the chains of polyuronic acids dissolved from the surface of the nanocrystals. The experiments revealed that the addition of sodium azide in an amount sufficient to prevent the development of microorganisms in the sample reduces the stability of the suspension.