Upper Cretaceous strata at Göynük, northwestern Anatolia, Turkey, provide a geological record of the Campanian–Maastrichtian from the Sakarya Terrane along the active Neotethys margin. Shales and shaly marls with siliciclastic and volcaniclastic intercalations indicate a pelagic palaeoenvironment rich in planktonic and benthonic foraminifera and calcareous nannofossil assemblages. A composite record from the Campanian to the Maastrichtian records nannofossil standard zones UC15c (CC21) to UC20a (CC26) as well as the Globotrunanella havanensis planktonic foraminifera Zone to the Racemiguembelina fructicosa planktonic foraminifera Zone. The complete ‘mid’-Campanian to early Maastrichtian composite section can be correlated to other western Tethyan sections. The Campanian–Maastrichtian boundary is positioned between the first occurrence of the planktonic foraminifera Gansserina gansseri and the last occurrence of the nannofossil Uniplanarius trifidus. Clastic input and higher sedimentation rates constrain regional sea-level lowstands around the late Campanian calcarata Zone and the Campanian–Maastrichtian boundary, corresponding to the Campanian–Maastrichtian boundary event.