A lean NOx trap (LNT) followed by selective catalytic reduction (SCR) without the urea injection system (LNT-urealess SCR, LNT-pSCR) has been developed to meet the stringent regulations on NOx emission. For the LNT-pSCR system to be commercialized, optimal design and control of the system are required. It is important to minimize the capital cost while satisfying the NOx regulation standards and minimizing fuel consumption. In this study, we propose a strategy to optimally design the lengths of the LNT and pSCR and tune control parameters by solving the multiobjective optimization problem and considering control logic simultaneously. For decision makers, NOx emission and capital cost are critical factors to consider. In addition, NH3 slip and fuel loss caused by post injection must be considered. The Pareto optimal points are obtained by solving the biobjective optimization problem with respect to NQ(x) emission and capital cost while the other factors are constrained. Among the Pareto optimal points, we suggest a set of design and control tuning parameters. To reduce NOx only by 0.41% more than the suggested system, the capital cost increases significantly by 21.82%. Meanwhile, the results of multi objective optimization without considering the control logic (fixed timings and durations of the rich modes) are trivial, in that the amount of NOx reduction increases as the volume of the LNT-pSCR system increases.