Molecular dynamics simulation was used to study the compressive deformation of austenite nanoparticles with a nanocrystalline structure at low temperatures. The authors studied the influence of nanoparticle size (from 2 to 20 nm) and crystalline grain size (from 2 to 8 nm) on their strength and on the value of compressive deformation at which maximum stress is achieved. The characteristics of plastic deformation in the case of nanoparticles with a nanocrystalline structure are highlighted. Uniaxial compression of the nanoparticle was simulated in the model by moving virtual planes on both sides of the particle with a constant velocity of 10 m/s at an initial temperature of 0 K. The study demonstrated that the nanoparticles strength decreases with decreasing average grain size. While the size of the nanocrystalline particles themselves decreases, as with single-crystal particles, their strength increases. The authors also found that with decreasing particle size, the value of deformation, at which maximum stress is achieved during nanoparticle compression, increases. A decrease in grain size leads to a decrease in strength, which is associated with the primary mechanism of plastic deformation of metal particles with a nanocrystalline structure: grain boundary sliding. During the first stage of deformation, the entire particle structure typically rotated until the maximum value of the stress vector projection onto the preferred shear plane was reached. In the case of a nanocrystalline structure, this was determined by the relative orientation of the grain boundaries. Grain boundaries, roughly aligned along the same plane, represented the preferred shear plane in this case.