The use of nonviral carriers based on nanomaterials is a promising strategy for modern gene therapy aimed at protecting the genetic material against degradation and enabling its efficient cellular uptake. To improve the effectiveness of nanocarriers in vivo, they are often modified with poly(ethylene glycol) (PEG) to reduce their toxicity, limit nonspecific binding by proteins in the bloodstream, and extend blood half-life. Thus, the selection of an appropriate degree of surface PEGylation is crucial to preserve the interaction of nanoparticles with the genetic material and to ensure its efficient transport to the site of action. Our research focuses on the use of innovative gold nanoparticles (AuNPs) coated with cationic carbosilane dendrons as carriers of siRNA. In this study, using dynamic light scattering and zeta potential measurements, circular dichroism, and gel electrophoresis, we investigated dendronized AuNPs modified to varying degrees with PEG in terms of their interactions with siRNA and thrombin to select the most promising PEGylated carrier for further research.