McAuley began his career playing in Northern Irish football with Linfield, Ballyclare Comrades, Crusaders and Coleraine before joining English side Lincoln City in the summer of 2004. He impressed enough at Sincil Bank to earn a move to Championship side Leicester City. He moved on to Ipswich Town in June 2008 following Leicester's relegation and then on to Premier League side West Bromwich Albion in July 2011. McAuley won West Brom's player of the year award for the 2012–13 season.
McAuley began his career at Linfield and spent some time in early 2000 on loan at Ballyclare Comrades. After four years at Linfield, he moved to Crusaders in the summer of 2000. After two successful seasons, he moved to Coleraine.
In the summer of 2004, McAuley decided the time had come to look for a move into full-time football in the Football League. After attracting interest from Lincoln City and Stockport County he linked up with Edgeley Park based club for a two-week trial under the eye of the former Northern Ireland manager Sammy McIlroy who had given McAuley his first Northern Ireland B call-up. After impressing in his trial, McAuley seemed set to sign for Stockport but talks broke down and he instead joined Lincoln City on a two-year deal with Coleraine receiving £10,000 for his services. With Lincoln already boasting one of the strongest defences in League Two at the time of McAuley's arrival, he did not walk straight into the first team. His first few appearances for the club were all as a substitute, and often in the role of a target man striker.
However, when Dean West was dropped from the squad and club captain Paul Morgan sidelined with an injury, McAuley moved into central defence to partner Ben Futcher. He immediately drew the plaudits for his excellent performances, which included a man of the match display against Derby County. He thereafter battled for a starting centre back role with fellow giant Jamie McCombe for much of the season.
However, in March 2005, McAuley earned a starting role as the right full-back, replacing the perpetually out of form fan favourite Matt Bloomer. He continued to play in this position for the rest of the season, helping Lincoln to the play-off final, not just with his exceptional defensive performances, but with 5 goals, including both in a 2–1 aggregate victory over Macclesfield in the play-off semi-final.
The 2005/2006 season, however, saw him cement a spot in the centre of the Imps defence. With Ben Futcher leaving on a free transfer to join rivals Boston United, McAuley took his place. He enjoyed a fantastic season, which culminated ultimately in play-off defeat for Lincoln again, but saw him named in the League Two Team of the Year, and also caught the attention of a number of bigger clubs.
The lure of playing at a higher level saw McAuley reject Lincoln City's offer of a new contract in the summer of 2006, and he moved on a free transfer to Leicester City.
McAuley signed for Leicester City on 5 June 2006, after reaching the end of his contract at Lincoln, signing a three-year deal. He scored his first senior goal for Leicester on 17 January in a 4–3 defeat to Fulham in the FA Cup, and was also on the scoresheet against Ipswich Town on 10 February, heading in both as Leicester won 2–0.
In the 2007–08 season, McAuley was appointed captain in a 0–0 draw against Wolves on 2 October 2007, following Stephen Clemence's injury. He scored his fourth goal on 5 October against Sheffield Wednesday, helping Leicester earn their second only league win of the season, and was then named in the Championship Team of the Week three days later. McAuley is one of three players (DJ Campbell & Carl Cort) who netted in three goals against Chelsea in a League Cup match on 31 October at Stamford Bridge, but could not prevent his side from losing 4–3.
In January 2008, Ipswich Town manager Jim Magilton made two bids to sign McAuley, but both of these were turned down. Despite signing a new three-and-a-half year deal on 8 February, McAuley decided to leave Leicester following their relegation three months later.
McAuley signed for Ipswich Town on 18 June 2008 and was named captain for the 2008/09 season. The defender got off to a somewhat shaky start, but after settling into the squad, established himself as a commanding leader and consistent defender. McAuley further enhanced his international credentials whilst with the Suffolk team. On 6 November 2010, McAuley played his 100th game for Ipswich Town, in which he scored the winner in a 2–1 win against Sheffield United.
On 23 May 2011, West Bromwich Albion officially announced McAuley would be signing a three-year contract (pending a medical) beginning 1 July; he scored his first goal for the team in a 3–2 win away at Newcastle in December 2011. McAuley scored his 2nd West Bromwich Albion goal by helping them beat Chelsea after 33 years without a point against the blues, he scored in the 82nd minute for the game to finish 1–0.
On 11 February 2013, McAuley scored his second goal of the Premier League season against Liverpool in a match that ended 2–0.
On 28 April 2013, Gareth was voted Players' Player of the Year and Supporters' Player of the Year after an impressive 2012/2013 season.
On 21 March 2015, McAuley was sent off in the second minute against Manchester City by referee Neil Swarbrick in a Premier League match, due to mistaken identity with Craig Dawson.
In May 2003, McAuley received his first senior international call when he was one of five Irish League players named in the squad for the Northern Ireland B team fixture with Scotland B on 20 May 2003. Selected in the starting eleven, the team fell to a 2–1 defeat in front of just 1,502 spectators at Firhill Stadium.
He received his first cap against Germany as his team lost 4–1 in a friendly match on 4 June 2005.
McAuley contemplated international retirement after being left out of the squad to face Sweden on 17 October 2007. But on 9 October, Nigel Worthington recalled him to the squad. McAuley made his comeback against Sweden on 17 October, drawing 1–1. He was also part of the squad that defeated Denmark 2–1 in a memorable victory on 17 November, keeping the national team's hopes of qualifying for the UEFA Euro 2008. Their hopes were dashed when they lost 1–0 to Spain in Las Palmas on 21 November, finishing third in Group F with twenty points. McAuley scored his first international goal against San Marino on 11 February 2009.
McAuley was called up to the Northern Ireland squad for the European qualification games against Serbia and Slovenia in March 2011. He scored his second international goal against Serbia, but could not prevent his side losing 2–1. For the second game, against Slovenia, McAuley was named captain for the first time. He led his side to a 0–0 draw, putting in a man of the match display himself at the same time.
On 4 September, McAuley scored twice for Northern Ireland in a 3–1 win against the Faroe Islands. The result put Northern Ireland at the top of Group F and on the brink of qualifying for their first European Championship.
McAuley scored the first Northern Ireland goal in a tournament for 30 years, since Colin Clarke at the 1986 FIFA World Cup, against Ukraine in Euro 2016. In addition to this making him the second-oldest scorer at the Euros, it also saw the team win for the first time at the European finals. Having made it out of the group stage, McAuley scored an own goal during the Euro 2016 round of 16 match against Wales, that resulted in Northern Ireland being eliminated from the tournament. At 36 years and 341 days, Gareth McAuley because the oldest scorer in European 2018 FIFA World Cup Qualification games when he scored the second goal in Northern Ireland's 4–0 win over Azerbaijan on 11 November 2016.As of match played 16 May 2017
Scores and results list Northern Ireland's goal tally first.