Born in Smithfield, Sydney, he joined the English Premiership football club Leeds United on trial at 16 from New South Wales Academy. He made his Leeds debut as 17-year-old on 30 March 1996 in a 1-0 home defeat by Middlesbrough. He made his Australia debut in April 1996 in 3-0 defeat by Chile.
Playing mostly in a left midfield role and in attack, he became Leeds' best player, eventually forming a striking partnership with fellow Australian Mark Viduka. The high point of this period was when they helped Leeds to the semi-final of the Champions League in 2000-01. Unfortunately, however, the club began to suffer financial difficulties and, by 2002-03, the efforts in front of goal of Kewell and Viduka prevented a mediocre Leeds side from being relegated from the Premiership.
Disillusioned with the plight of cash-strapped Leeds, Kewell moved to Liverpool for the start of the 2003-04 season. The transfer was highly controversial, with claims that Liverpool paid Kewell's agent a substantial fee to ensure that he ended up at Anfield.
Kewell has not always turned out for Australian national team, but when he has his efforts have been outstanding, scoring on a regular basis against strong teams and helping in victories against France, Brazil, and — probably more importantly to most Australians — against England.