A transmission matrix method (TMM) commonly used for modeling the electromagnetic properties of multilayered biopolymer/conductive nanoparticle composites is presented, which predicts the behavior of the experimental results of the electromagnetic shielding effectiveness of a deoxyribonucleic acid-silver nanoparticle composite but falls short for accurately predicting the absolute shielding effectiveness. The versatility of the model can handle metamaterials, various incident angles, both TE and TM polarizations, and single and multilayer structures with complex and dispersive permittivity and permeability. We present the simulated results for a single-layer slab using the TMM along with the experimental results. Parametric studies are conducted with the model to investigate the reflection and transmission performance for single-layer slabs by varying the loss tangent, dielectric constant, incident angle, and thickness parameters.