The documentation of proteinaceous soft tissues in fossils from deep time remains controversial. Often this has been attributed to the laboratory or other modes of modern contamination. Here we provide incontrovertible evidence for the preservation of proteinaceous moieties in the Maastrichtian dinosaur eggshells using pyrolysis-GC×GC-TOFMS. The presence of nitrogen-bearing organic molecules along with diketodipyrrole suggest that the proteinaceous moieties can survive diagenesis. The preservation of these proteinaceous moieties has been attributed to deposition in a palustrine flat environment under subaerial conditions and entrapment of organic material by the eggshell calcitic units. The present study demonstrates that the preservation of nitrogen-bearing macromolecules in Mesozoic fossil remains is not impossible provided the depositional environments and diagenetic processes are propitious. The survival of nitrogen-bearing macromolecule in deep time under subaerial depositional settings will open a new avenue to the research on soft tissue preservation.