This paper reports the findings of a detailed study of the self-assembly of gold nanoparticles at the surface of carbon nanotubes (CNTs). The study included the development of a predictive model for the interactions (charge transfer, van der Waals, osmotic, elastic, nonelastic, and covalent) between tetraoctylammonium bromide-stabilized (TOAB) gold nanoparticles and alkyl- and alkylthiol-modified multiwalled carbon nanotubes (MWCNTs). It also included the measurement of the coverage of gold nanoparticles at the surface of the above MWCNTs as a function of increasing alkyl chain length. One key finding is that it is possible to predict with a high degree of accuracy using the above model the measured coverage of gold nanoparticles adsorbed, either noncovalently or covalently, at the surface of a MWCNT. Another key finding is that, as predicted, under well-defined conditions the measured coverage of nanoparticles is very sensitive to the nature of the modified CNT surface and the contiguous environment, providing valuable insights that will underpin the rational design of functional nanoscale devices assembled front nanoparticle and CNT building blocks.