Gold nanoparticles exhibit an array of properties, both intrinsic (chemical) and extrinsic (photothermal), that can be exploited for their use in cancer therapeutics. Owing to their size and ease with which they can be functionalized with various ligands, gold nanoparticles represent a class of highly functional biomedically relevant nanostructures. Here, we explore the use of gold nanoparticles as intrinsic (chemical) antineoplastic agents, with their ability to cause DNA damage and cytokinesis arrest, to induce apoptosis in a metallic composition-dependent manner, as well as their ability to enhance sensitivity to chemotherapy by regulation of the cell cycle. The extrinsic (photothermal) properties of gold nanoparticles are also examined, in detail, through both theoretical and experimental assessment, for their use as photothermal contrast agents in vitro. Based on this assessment, the gold nanoparticles are tested in the plasmonic photothermal therapy of head and neck cancer in a mouse model.