Geraerts played for Club Brugge from 1998 to December 2003. In 2004 Club Brugge lent him to Lokeren where he scored his first goal in the Jupiler League. In the summer of 2004 he moved to Standard Liège. In June 2007 he went back to Bruges. As a youngster the midfielder played with C.S. Mechelen-aan-de-Maas and Racing Genk (from 1996 to 1998) before he moved to the youth team of Club Brugge. After the 2010-11 season, Geraerts was no longer part of the plans at Club Brugge and was told he could look for a new club, which resulted in him signing with newly promoted side Oud-Heverlee Leuven on the last day of thetransfer period.
In 2005, Geraerts debuted for the Belgium national football team. In his first match in the starting line-up, on 12 October in and against Lithuania in a World Cup qualifier, he scored the opening goal.