A computational method to determine the shielding effectiveness against electromagnetic interference of carbon nanotube (CNTs)-based nanocomposites through modelling of its electrical properties is presented. Specifically, simulations based on Ant Colony Optimization (ACO) were implemented to evaluate the electrical conductivity (sigma) of CNTs (used as a filler in a polymer matrix) that formed electrical network inside a representative cuboid volume of the sample. A pseudo three-dimensional (3D) percolation model was developed to study the effects of random connectivity of CNTs to one another on the conductivity of nanocomposites. In our approach, both contact and intrinsic resistances were taken into account. The tunneling resistance between CNTs was also taken into account while dealing with single-walled CNTs (SWCNTs). A resistor network recognition method that optimizes connective paths was built using ACO method and conductivity was subsequently computed as a function of CNTs concentration. Then, the shielding effectiveness was computed using the conductivity data. It is remarkable that the calculated SE values as a function of frequency of EM waves at a constant weight percent of CNTs were in agreement with the experimental data for CNT-based nanocomposites reported in literature. (C) 2016 Elsevier B.V. All rights reserved.