<p>The results of computational and experimental research on the influence of electrically conductive carbon black (CB) on the elastic modulus of composites based on linear low-density polyethylene (LLDPE) were presented. The study was carried out at various structural levels of composites: a cell with a single filler particle, a cell with randomly distributed filler particles, a composite with randomly distributed agglomerates, and a macro level of a composite. The results show that the agglomeration of filler with a low local content reduces the elastic modulus of the composite, while the agglomeration of filler with a high local content increases it. In the LLDPE+CB composites, the filler has a complex influence on the elastic modulus of the composite. The values of elastic modulus of the composite were influenced by both single CB particles and an agglomerated filler with an increased local content in the matrix. As a result, the elastic modulus of the LLDPE+CB composites at the macroscale level increases nonlinearly with increasing filler content.</p>