Hargreaves was born in Cleethorpes, Lincolnshire, and went to school at Lindsey School in Cleethorpes. He began as a youth team player at Everton but came back to his home town club Grimsby Town as a trainee with June 1988, turning professional in December 1989. He had a loan spell with Scarborough in March 1993, before leaving Grimsby to join Hull City in July 1993 for a fee of £50,000.
He moved to West Bromwich Albion on a free transfer in July 1995, but made just two first team appearances for the Baggies (both as a substitute). He joined Hereford United on loan in February 1996 until the end of the season when he moved to Hereford on a free transfer. His next move was in July 1998 when he joined Plymouth Argyle on a free transfer. He was a regular in the Argyle side, leaving to join Northampton Town on a free transfer in June 2000. He was Northampton's player of the year in the 2001-02 season, signing a new two-year contract in July 2002.
Hargreaves made over 150 league appearances for Northampton, leaving to join Brentford in June 2004. Hargreaves joined Oxford United on free transfer in July 2005, remaining with Oxford after their relegation to the Conference in 2006. He was released by Oxford in May 2007, signing for newly relegated Torquay United the following month. On 17 May 2009, he scored Torquay's first goal as he captained them in a 2–0 victory over Cambridge United in the Conference National play-off final at Wembley. The victory earned them promotion to The Football League.
In January 2010 Hargreaves completed a return to Oxford United, where he won promotion out of the Conference for the second successive season.
On 6 January 2014, Hargreaves was appointed as Torquay United manager. Hargreaves was unable to keep Torquay in the Football League despite an upturn in form and performances. He left the club in June 2015 after failing to agree terms on a new contract and was subsequently replaced by Paul Cox.