Hamann played for Germany at under-21 level before making his full international debut in a friendly against South Africa in November 1997. He was selected by manager Berti Vogts for the 1998 FIFA World Cup, being, at almost 25, the second youngest player in an over-aged Germany squad. During the group stage, Hamann drifted in and out of the starting XI, finally breaking into the team when Germany gained momentum in the second round game against Mexico. However, after a quarter-final defeat against Croatia, Germany was out of the tournament.