[1] On 30 August 1996, already having started the campaign with Köln, Illgner was signed by Real Madrid, and played 40 La Liga matches in his first year to help the capital side to the national championship conquest.

In the following he lost his place to Santiago Cañizares,[2] but regained it in time to play in the final of the UEFA Champions League against Juventus FC (1–0 win).

[5] 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.

[6] Overall, Illgner appeared 54 times for his country, and also played at the 1994 World Cup, surprisingly retiring after the quarter-final loss against Bulgaria although he was only 27.