In this work, by the example of the system of linear low-density polyethylene-multi-walled carbon nanotubes (LLDPE/CNTs), specific features of the nanocomposite structure modified by severe plastic deformation (SPD) are studied. The effect of SPD on the mechanical properties and electrical conductivity is analyzed. It is shown that SPD leads to destruction of CNTs aggregates and more homogeneous their distribution. CNTs formed structure is characterized by the presence of large (200-300 nm) aggregates of CNTs and small (<100 nm) CNTs aggregates. It is found that within the range of a small degree of strain (up to e = 4.4), rupture is the prevailing mechanism of agglomerate disintegration, and erosion dominates in the range of high strain (e = 4.4-8.5). SPD-induced formation of a 3D-conducting network of CNTS and strengthened LLDPE matrix determines an enhanced set of electrical and mechanical characteristics of the tested composites. POLYM. ENG. SCI., 59:714-723, 2019. (c) 2018 Society of Plastics Engineers