Structures are often subjected to sequences of mainshock and aftershocks during their service life. Strong aftershocks have been known to cause extensive structural damage and losses of human lives in addition to the damage and losses of the mainshock. Steel plate shear walls (SPSWs) have recently attracted considerable interest as a promising lateral-resisting system in seismic-prone regions. The SPSWs consist of steel beams and columns with a thin infill steel plate. The unstiffened thin plates are expected to buckle at low seismic loads and develop tension field action that enables favorable ductility and energy dissipation. The American Institute of Steel Construction's Seismic Provisions prescribe a capacity-based design methodology that uses SPSWs as primary seismic force resisting systems, and require the design of SPSWs to be consistent with the design requirements for other ductile steel seismic force resisting systems. This paper presents numerical analysis of a code-designed eight-story SPSW building that was subjected to consecutive mainshock-aftershock earthquake events. Ground motions developed for the SAC project were selected and scaled to simulate the main shock events at maximum considered earthquake (MCE) level, and large aftershocks events at design base earthquake (DBE) level. Nonlinear response history analysis using the finite element program OpenSees were conducted to investigate the performance of the code designed SPSWs. It was demonstrated that the designed SPSW has good performance under mainshock-aftershock sequences.