The sector of Antarctica facing Australia east of 139 °E is characterized by the abundance of exceptionally long oceanic fracture zones that are collinear to post-rift right-lateral strike–slip fault systems developed at the northeastern edge of the Antarctic continent. High-resolution reflection seismic profiles indicate recent strike–slip activity at the southeastern edge of the Balleny Fracture Zone, similar to what is observed onshore in North Victoria Land. The architecture, kinematics, and timing of this intraplate deformation at the northeastern edge of Antarctica cannot be reconciled with typical plate tectonic kinematics, in particular, with a classical divergent plate boundary environment. Here we show that combined geological and geophysical data in northeastern Antarctica support the post-rift southeastward reactivation of the passive margin east of 139 °E along intraplate right-lateral strike–slip deformation belts. These deformation belts include oceanic transform faults and their collinear oceanic fracture zone and continental shear zone extensions. A striking consequence is that there is intraplate accommodation of transform fault slip in this region of Earth's surface along fracture zones and a long-active region of intracontinental deformation that is ‘reusing’ prior plate boundary fault zones. As the intraplate termination of plate boundary transform faulting is not predicted by classical plate tectonic theory; this region is one of the most clear examples of the transition from rigid to semi-rigid plate tectonic deformation during the formation and long-lived incubation of a potential new plate boundary.