Growing up in Macquarie Fields, Emerton first played for Gunners Soccer Club at Bensley Road as a five-year-old. He was nicknamed 'the greyhound'. During the following years he played for the Macarthur Rams.
Emerton was a product of the Australian Institute of Sport and started his career with Sydney Olympic in the National Soccer League in August 1996. During his stay at the club he impressed widely with his pace and stamina, as much as his play with the ball. After making 94 appearances and scoring 16 goals. Emerton began to be noticed in Europe.
After captaining the Olyroos at the Sydney Olympics, Emerton joined Feyenoord in August 2000 for a fee of £415,000, winning a UEFA Cup winners medal in May 2002. (although Emerton himself was banned for the final match) and being named the 2002 Oceania Footballer of the Year. He made a total of 111 league and cup appearances for Feyenoord, scoring eleven goals.
After being linked with several Premiership teams, Emerton eventually joined Blackburn Rovers in July 2003 for an undisclosed fee, on a four-year contract, saying, "I've always dreamed of playing in the Premiership so to finally achieve it is great." He turned down offers from other clubs so that he could play in his preferred position on the wing. He scored on his debut in a 5–1 win over Wolverhampton Wanderers in August 2003. Manager Graeme Souness said of him: "Emerton is a top player. If he can keep up that level of trickery I will be quite happy." In his first Premier League season, Emerton played in 37 league games, scored 2 goals, and featured in 40 matches in all competitions. However, Blackburn failed to make progress in the UEFA Cup and struggled against relegation.
Blackburn survived that season but again struggled in the 2004–05 season, not winning a game until September 2004. However, the club preserved their Premiership status following a change of manager and reached the FA Cup semi-finals, where they lost to Arsenal. Emerton paid credit to new manager, Mark Hughes, "It is a huge achievement. When Mark came in we were in a bit of disarray but from the day he arrived we worked on our fitness. Everyone is better for that and it has shown in our performances."
A more successful season in 2005–06 saw Blackburn reach the 5th round of the FA Cup, losing to West Ham United, the semi-finals of the Carling Cup and qualifying for the UEFA Cup. Following the end of the season, Emerton signed a new four-year deal at Blackburn in August 2006. Mark Hughes described him as "...a player who gives me a lot of options. He can carry the ball from one end of the field to the other. That's why teams have coveted him this summer." Emerton made 47 appearances in the 2006–07 season as Blackburn finished in mid-table but reached the FA Cup semi-final for the second time in three years, losing to Chelsea, and reached the knock-out stages of the UEFA cup, eventually losing out to Bayer Leverkusen for a place in the last 16. At the end of the 2006–07 season, Emerton had made a total of 167 appearances for Blackburn in all competitions, scoring 10 goals.
In July 2008, Emerton signed a new four-year contract, keeping him at the club until the summer of 2012.
On 31 January 2009, Emerton's 2008–09 season came to a halt versus Middlesbrough when during a tackle, he damaged his knee. It was revealed on 2 February that he had damaged his cruciate ligament, which meant he would miss the remainder of the season, 6 to 9 months being his expected recovery time.
On 12 September 2009, Emerton made his long-awaited return to Premier League football as a second-half substitute in the 3–1 Blackburn victory over fellow Premier League side Wolverhampton Wanderers. On 4 October 2009, Emerton started his first match in 2009–10 since being injured at Middlesbrough the previous season, playing against Arsenal at the Emirates Stadium in a heavy 6–2 defeat with Emerton playing 57 minutes before being replaced by substitute Morten Gamst Pedersen. In all competitions during the 2009–10 season, Emerton made a total of 29 appearances, scoring two goals, and providing four assists.
On 25 July 2010, he replaced Morten Gamst Pedersen in the 60th minute in the 2–1 defeat to Rangers in the Sydney Festival of Football tournament held in Australia, but could not prevent the team from losing. "The biggest cheer of the afternoon came on the hour mark with the introduction of Brett Emerton, the Australian crowd all standing to applaud the introduction of the Sydney-born midfielder. Emerton scored his first goal of the 2010–11 Premier League season in a 2–1 victory over Blackpool at Bloomfield Road on 25 September, in which he scored in the 92nd minute of injury time. On 4 December, he scored his second goal of the season at Ewood Park against Wolverhampton Wanderers in the 43rd minute, playing the full 90 minutes in a 3–0 victory. Emerton scored the opening goal, and his third goal for the 2010–11 season, against local rivals Manchester United. In Rovers' last Premier League match of the season against Wolves at Molineux, Emerton scored a volley on 38 minutes and also played the full 90 minutes in a 3–2 win. He was made captain for his final match for Blackburn against Everton at Ewood Park on 27 August 2011, playing the full 90 minutes.
On 25 August 2011 it was announced that Emerton had signed with two time A-League champions, Sydney FC on a three-year deal after terminating his contract with Blackburn Rovers by mutual consent returning him to his homeland after 11 years abroad. He was the Vice-Captain of Sydney FC. He made his début at Etihad Stadium against A-League giants Melbourne Victory, where he had a 33rd-minute penalty saved by Ante Covic and came off in the 84th minute in front of 40,000 people in attendance in the 0–0 draw. He scored his first goal in the round 7 game against the Central Coast Mariners from a free kick, but Sydney slumped to a 3–2 defeat.
0n 23 March 2013 Emerton was shown a red card against Western Sydney Wanderers for a studs-up challenge on left-back and former teammate Shannon Cole. He received a straight red card even though he received a yellow card three minutes before.
On 20 July 2013, Emerton captained the A-League All Stars in the inaugural A-League All Stars Game against Manchester United, a match in which the A-League All Stars were thrashed 5–1, courtesy of goals from Danny Welbeck, Jesse Lingard and Robin van Persie. Emerton was substituted off in the 83rd minute of the match, and was replaced by Adelaide United midfielder Marcelo Carrusca.
On 16 January 2014, Emerton announced his retirement from professional football as a result of his persistent back problems.
Emerton was captain of the "Olyroos", Australia's Olympic football team, at the 2000 Summer Olympics in Sydney, where he was sent off against Nigeria as Australia were beaten 3–2 and went out of the tournament. He was named in the Australia squad for the Fifa Confederations Cup held in South Korea and Japan in 2001 and made the starting line-up in a shock win over France and a defeat by South Korea as Australia qualified from the Group stages.
Emerton was a member of the Australian national team that lost out on the final place in the 2002 World Cup finals in Korea and Japan when Uruguay beat Australia over two legs in November 2001. He played in the team that comprehensively beat England 3–1 at the Boleyn Ground in February 2003, scoring the final goal to seal an impressive win.
Emerton played in both legs of World Cup play-off against Uruguay in November 2005, when the Socceroos qualified for the 2006 FIFA World Cup in Germany, the first time that Australia had reached the finals of the World Cup since 1974, and was named in the Australian squad for the World Cup finals. He was in the starting line-up for all three Group Stage games against Japan, Brazil and Croatia as Australia qualified for the second round. However, he received two yellow cards against Croatia, was sent off in the 87th minute and subsequently missed the Socceroos' second round match against Italy.
Emerton scored two goals against Qatar in Australia's fourth match of World Cup Qualification for the 2010 FIFA World Cup, in Doha. The match finished 3–1 to the Australians, as the nation advanced to the second round of the World Cup qualifiers. He also scored two goals against Qatar on 15 October in Brisbane, one from the penalty spot and the other a right foot finish from a flowing Australian move. Since returning from injury Emerton has received an international recall for the upcoming matches against the Netherlands and Oman. In his return match for the Socceroos against the Netherlands, Emerton came on as a second-half substitute for Josh Kennedy, and made an exceptional return by looking dangerous on the right side of midfield. He then started the next match on against Oman and played a full 90 minutes. Emerton scored a late winner against Oman in the 2011 Asian Cup Qualifying fixture to give the Socceroos a 2–1 win. On 17 November 2010, he injured his hamstring whilst on international duty against Egypt in a 3–0 defeat in Cairo. On 25 January 2011, Emerton scored his 18th goal for his country and the fourth goal in the 73rd minute of the match when he scored against Uzbekistan in a 6–0 win in the semi-finals of the 2011 AFC Asian Cup after coming on from the bench. He played a total of 5 games at the tournament. On 5 June 2011, he captained the Aussies because there was no Lucas Neill in their 3–0 victory over rivals New Zealand at the Adelaide Oval Stadium. On 7 June 2011, Emerton started the friendly game against Serbia playing in the 0–0 draw. Emerton started and scored the winner in a 1–0 victory for the Socceroos against Hong Kong in East Asian Cup qualification.
1 - Includes FA Cup, League Cup and FA Community ShieldScores and results list Australia's goal tally first.
UEFA Cup: 2001–02
OFC U-17 Championship: 1995
OFC U-20 Championship: 1997
OFC Nations Cup: 2000, 2004
NSL U21 Player of the Year: 1997–98
Oceania Footballer of the Year: 2002
A-League All Stars: 2013