The end-Cretaceous mass extinction has been attributed by most to a single asteroid impact at Chicxulub on the Yucatán Peninsula, Mexico. The discovery of a second smaller crater with a similar age at Boltysh in the Ukraine has raised the possibility that a shower of asteroids or comets impacted Earth close to the Cretaceous-Paleogene (K-Pg) boundary. Here we present palynological and δ13C evidence from crater-fill sediments in the Boltysh impact crater. Our analyses demonstrate that a post-impact flora, formed on the ejecta layer, was in turn devastated by the K-Pg event. The sequence of floral recovery from the K-Pg event is directly comparable with that in middle North America. We conclude that the Boltysh crater predated Chicxulub by ∼2–5 k.y., a time scale that constrains the likely origin of the bodies that formed the two known K-Pg craters.