We constructed a rupture model of the 2017 8.2 Chiapas, Mexico, earthquake by incorporating teleseismic waveform data and static Global Positioning System (GPS) displacements and analyzed the transient postseismic deformation. The high‐slip coseismic rupture region spanned along strike and along dip, with a peak slip of 11.6 m, mean stress drop of , and seismic moment of ( 8.2). After six months, postseismic deformation was mainly dominated by afterslip concentrated in several patches around the coseismic rupture, which was consistent with aftershock locations and previous observations of afterslip following large earthquakes. Aftershocks can be mostly explained by Coulomb failure stress (CFS) changes induced by the mainshock rupture and afterslip process. We found that afterslip released approximately 54.7% of the coseismic moment and was accommodated aseismically and seismically by aftershocks, indicating that aftershocks were likely driven by afterslip following this great intraplate event. Our results provided important insights into the seismogenic structure and mechanisms for stress accumulation and release in the Mexican subduction zone.