Gold nanoparticles (AuNPs) can interfere with some of the biochemical processes of macrophage cells but the mechanisms of action of these potentially medically-relevant effects are still unclear. Here we study the fate of AuNPs interacting with cells derived from the innate immune system. To visualize AuNPs with nanometer resolution without losing sight of the whole morphology of cells we developed a convenient approach that uses electron and ion microscopy techniques. The inspection using an ion beam to selectively cut where the AuNPs were found, allows for determining their intracellular localizations. We studied the cellular uptake of AuNPs, with or without exposure of the cells to Latrunculin-A, a phagocytosis inhibitor. Results indicate a size dependence of the internalization mechanisms for THP-1 cells. The internalization of larger AuNPs was blocked in the presence of Latrunculin-A, although they could attach to the membrane. Smaller AuNPs though were not blocked by actin depending processes.