The end-Permian mass extinction is marked by pronounced terrestrial ecosystem turnover and a severe loss of marine invertebrate biodiversity. This extinction event is accompanied by a prominent negative carbon-isotope excursion indicating massive changes in the global carbon cycle across the Permian-Triassic boundary. In this study, we present organic carbon-isotope data from land plant cuticles, fossil wood fragments, and bulk organic matter recovered from the Amb section in the Salt Range, Pakistan. We apply δ13C data from cuticles as a proxy record for the carbon-isotope composition of atmospheric CO2 across the Permian-Triassic boundary. The data show an ∼5.5‰ negative excursion in terrestrial organic matter, reflecting the change in carbon-isotope composition of atmospheric CO2. Our data demonstrate that these atmospheric changes coincide with biotic (mass extinction) and abiotic (carbonate carbon-isotope perturbation) changes in the marine realm, hence affecting the entire ocean-atmosphere system.