The catalytic ozonation of diclofenac (DCF) with iron silicate-loaded pumice (FSO/PMC) in aqueous solution was investigated. FSO/PMC was synthesized by a co-precipitation–impregnation method and characterized using scanning electron microscope, N2 adsorption–desorption, X-ray fluorescence, and pHpzc measurements. Results showed that the FSO/PMC/O3 process obviously improved total organic carbon (TOC) removal efficiency from 32.3% (using sole ozonation) to 73.3% in 60 min. DCF mineralization in various oxidation processes was found to follow a two-stage pseudo-first-order kinetics. The presence of FSO/PMC effectively improved the mass transfer of ozone from gas to liquid phase and increased the efficiency of ozone decomposition, which results in the formation of •OH radicals. The ozonation of DCF generated large amounts of the ozone-refractory carboxylic acids, and these compounds were found to be continuously removed in the FSO/PMC/O3 process due to the catalytic activity of FSO/PMC. The synergetic effect between ozonation and FSO/PMC adsorption indicated that FSO/PMC is a promising catalyst for the ozonation process.