Structural inversion refers to the reverse reactivation of extensional faults that influence basin shorteningaccommodated by contractional faults or folds. On the Korean peninsula, Miocene inversion structures have been found,but the Cretaceous rocks on Geoje Island may have undergone inversion as early as the Upper Cretaceous. To evaluatethe structural inversion on Geoje Island, located on the eastern side of South Korea, and to determine the effects of preexistingweakness zones, field-based geometric and kinematic analyses of faults were performed. The lithology of GeojeIsland is dominated by hornfelsified shale, siltstone, and sandstone in the Upper-Cretaceous Seongpori formation. NE andNW-oblique normal faults, conjugate strike-slip (NW-sinistral transpressional and E-W-dextral transtensional) faults, andNE-dextral transpressional faults are the most prominent structural features in Geoje Island. Structural inversion on GeojeIsland was evidenced by the sinistral and dextral transpressional reactivation of the NW and NE-trending oblique normalfaults respectively, under WNW-ESE/NW-SE compression, which was the orientation of the compressive stress during theLate Cretaceous to Early Cenozoic.