The modification of graphene nanoplatelets (GNPs) was carried out by oxidative polymerization of aniline. The effect of carbon template content and initial acidity of the reacting mass on the temperature profile of the reaction taking place, changes in pH and the nature of polyaniline (PANI) deposition were analyzed. The synthesized composites were studied by Raman spectroscopy. Interactions between the PANI molecules and the GNP surface were estimated by a molecular dynamics method. The PANI percent yield was found to be 84-94 wt.%, and it does not depend on the acidity of the medium at pH ≤ 2.0. The increase in the PANI content promotes generation of oligomeric products of the oxidative polymerization. Besides, it was established that the hydrogen groups are formed between the sulfonate groups present on the GNP surface and the amino groups of the PANI macromolecules, thereby leading to the stabilization of the modifying layer and contributing to the irregularity (non-uniformity) of the latter.