In this study, multi-objective optimization is performed for a reactor producing ethylene oxide from ethylene. The optimization considered three objectives: the maximization of the ethylene oxide production and selectivity, and the maximization of a safety factor related to the presence of oxygen in the reactor. The Pareto domain for this optimization problem was first approximated using the Objective-Based Gradient Algorithm, and the Pareto-optimal solutions were ranked using the Net-Flow procedure to determine the best operating conditions. From the optimization results, it is recommended that the ethylene oxide reactor be operated at high inlet pressure and gas temperature, and low inlet volumetric gas flowrate and chemical reaction moderator concentration. These operating conditions led to the highest ranked compromise solution, balancing the trade-off between each of the three objectives. Finally, it was found that a decrease in the inlet pressure or variation in the volumetric gas flowrate could readily lead to operating conditions outside of the Pareto domain, and these input variables should therefore be carefully controlled throughout operation of the reactor.