Neill's father moved to Australia from Northern Ireland, where he had played for local football clubs Brantwood F.C., Linfield F.C., and Cliftonville F.C.

[2] Neill grew up in Manly, Sydney and was a student at Wakehurst Public School in Belrose and St Augustine's College in Brookvale, before attending the Australian Institute of Sport on a football scholarship in 1994–95.

[5] In September 2001, Neill, by then the longest serving player at the club, submitted a transfer request[4] and shortly after, signed for Blackburn Rovers for an initial fee of £600,000 plus up to £400,000 more depending on appearances.

Carragher, a popular home-grown Liverpool player, was sidelined for six months and the incident sparked a war of words between Gérard Houllier and Graeme Souness after Neill and his manager did not apologise for 48 hours.

[citation needed] Johan Neeskens, who became assistant to Barcelona manager Frank Rijkaard for the 2006–07 season, said that Neill "could play for any of the best clubs".

[13] Neill was accused of his primary motivating factor being money, but he later refuted these claims, stating the move was for purely footballing reasons.

[19] On 17 September 2009, Neill joined close friend[20] Tim Cahill at Everton on a free transfer, signing a one-year deal.

Neill played his first game for Everton on 23 September 2009 in the League Cup, coming on as a second half substitution for Leighton Baines, in their 4–0 victory over Hull City.

[22] Neill's first start for Everton in the Premier League was on 25 October 2009 where he played a full match against Bolton Wanderers setting up two goals.

Neill made his Turkish Super Lig debut for Galatasaray on 24 January 2010 in a 1–0 home win at the Ali Sami Yen Stadium against Gaziantepspor.

[35] On 24 February 2014 Neill signed for Championship team, Watford for the remainder of the 2013-14 season,[36] but made only one appearance, as an 84th-minute substitute in a 3–0 home win against Barnsley on 15 March before being released in June 2014 effectively ending his career as a player.

[37] Not needed for cover as Watford's injury worries eased, Neill moved to Doncaster Rovers on 26 March 2014 on a loan until 22 April 2014,[38] subsequently extended for the remainder of the 2013–14 season.

[40] In October 1996, Neill became the third-youngest player, after Duncan Cummings and Harry Kewell, to debut for the Australian national team[41] when he played in a friendly game against Saudi Arabia in Riyadh, aged 18 years and 7 months.

In the closing minutes of Australia's Round of 16 game against Italy, he was involved in a controversial incident, as referee Luis Medina Cantalejo adjudged Neill to have fouled Italian full back Fabio Grosso in the penalty area.

Francesco Totti converted the ensuing penalty kick to score and give the Italians a 1–0 victory, knocking Australia out of the cup.

Neill responded to the criticism, refusing to contemplate retirement, instead appearing to lay the blame at the feet of the younger players of the squad.

On 6 May 2014, it was revealed that Socceroos team boss Ange Postecoglou had advised Neill that he would not be part of Australia's squad at the 2014 World Cup.

[58][59] On 20 November 2023, at Preston Crown Court, Neill was found not guilty of purposefully hiding money from his bankruptcy proceedings.