Targeted, reductive photodeposition of catalytic metals via plasmonic hot electrons excited on an electrode is a promising, economical approach to manufacturing plasmon-sensitized photoelectrodes for catalysis applications. This work examines liquid-phase, anisotropic photodeposition of Pt(0) co-catalysts from chloroplatinic acid, Pt(IV), onto suspended Au nanorods under localized surface plasmon (LSP) excitation. Photochemical Pt(0) nucleation is initiated by plasmonic hot electrons, which migrate to the Au surface according to the plasmon polarity. In situ, time-resolved absorbance monitoring of the photochemical reaction elucidated Au nanorod surface functionalization with Pt(IV), Pt(0) growth kinetics under Au LSP excitation, and the evolving light-matter interactions. Energy dispersive spectroscopy (EDS) mappings show preferential Pt(0) deposition on the Au nanorod ends, consistent with the laser-induced LSP dipoles. Discrete dipole approximation (DDA) of Maxwell’s equations corroborated measured optical responses and allows a priori design of hot electron energetics. Electronic valence band structure of the Pt-functionalized Au nanorod was measured by x-ray photoelectron spectroscopy (XPS) and calculated by density functional theory (DFT) to enumerate the energy distribution of carriers accessible for surface chemistry. Together, these techniques and analyses accelerate development of plasmon-sensitized photoelectrodes for solar fuel generation.