The objective of this study was the development of a fully mechanistic model for describing the degradation of free and copper-complexed cyanide and the evolution of degradation byproducts in a continuous flow completely mixed ozone contactor. The developed model incorporated mechanisms describing rate and extent of ozone mass transfer from gaseous to aqueous phases, comprehensive consideration of ozone self-decomposition reactions in the aqueous phase, and interactions of aqueous phase ozone and hydroxyl radicals with free and copper-complexed cyanide and byproducts of their degradation. Simulation of the effect of changes in influent gaseous ozone concentration, scavenger concentration, liquid flow rate, and influent pH on free and copper-complexed cyanide degradation was accompanied by explanation of simulation results based on the current understanding of aqueous ozone chemistry with respect to cyanide degradation. Experimental work included the operation of a laboratory-scale continuous-flow completely mixed ozone contactor for determining the rate and extent of cyanide degradation and byproduct evolution under various conditions. Experimental data was compared with results obtained from a model simulation carried out under similar conditions for validation of the developed model.