© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Density evolutions of dislocations and atomic vacancies in copper single crystals subjected to cyclic loadings are numerically evaluated by combining theoretical models for vacancy generation and dislocations’ behaviour during plastic slip deformation. Parameters for the model of dislocation movement, accumulation and annihilation are set so as that they mimic dislocation movement in regions without or with dislocation substructure in crystals. Cyclic stress–strain curve, evolutions of statistically stored dislocations and atomic vacancies are examined in detail. Atomic vacancy densities after 15 cycles of tensile/compressive loading of ± 3% axial strain amplitude reach 1024–1025 m−3, depending on the dislocations’ mean free path and aspect ratio of dislocation loops. Results agree well with experimentally obtained data in the literature.