On 23 September 1987, Illgner made his debut for the West Germany national team in a 1–0 friendly home win against Denmark, and went on to back Eike Immel during UEFA Euro 1988. At the 1990 FIFA World Cup he, by now the country's first-choice, was in exceptional form, and commanded the backline which consisted of the experienced Klaus Augenthaler, Andreas Brehme, Thomas Berthold, Guido Buchwald and Jürgen Kohler (with Matthias Sammer taking Augenthaler's place at Euro 1992); in the semi-final, he saved a Stuart Pearce shot in the penalty shootout against England, and his team would overcome Argentina in the deciding match, where he would keep a clean sheet in the 1–0 success.