Postecoglou was born in Athens, Greece. After Postecoglou's father, Jim, lost his business following the 1967 Greek military coup, Postecoglou emigrated to Australia by boat in 1970 at the age of five, growing up in Melbourne, Victoria. In his early years he grew up playing Australian rules football and is a lifelong supporter of the Carlton Football Club in the Australian Football League. Postecoglou supports Liverpool. Postecoglou is married to Georgia, who worked at South Melbourne as a marketing manager when he served as manager of the club. Postecoglou has two sons, James and Max.
After first joining the club as a nine year old, Postecoglou played 193 games from 1984 to 1993 for South Melbourne in the National Soccer League, where he was involved in their 1984 and 1990–91 titles, the latter as captain, before moving into coaching.
In his international playing career, Postecoglou represented Australia on four occasions between 1986 and 1988 as well as representing Australia at youth level in 1985.
Postecoglou coached South Melbourne from 1996 until 2000. He led them to consecutive National Soccer League titles in 1997–98 and 1998–99, as well as winning the 1999 Oceania Club Championship, which in turn led to their participation in the 2000 FIFA Club World Championship. After the 1999–2000 NSL season, he stood down from the South Melbourne coaching role when he was appointed coach of the Australian youth team. He is the only person to have been involved in all four of South Melbourne's NSL title-winning teams, the first two as a player and the latter two as coach.
Following his domestic coaching success, Postecoglou became coach of Australia's youth sides in 2000. During his tenure, he played a role in identifying and developing Australian players. Postecoglou was involved in an on-air argument with football pundit Craig Foster on The World Game. He was replaced as coach in February 2007 after Australia failed to qualify for the 2007 FIFA U-20 World Cup. After his departure as coach of the Australian youth teams, Postecoglou worked as a football pundit for Fox Sports and as an elite consultant to Football Federation Victoria.
Postecoglou coached the third division Greek club, Panachaiki Patras, from March 2008 to December 2008.
On 16 October 2009, Postecoglou was signed as the new Brisbane Roar coach, replacing Frank Farina. Postecoglou started rebuilding the team by getting rid of Liam Reddy, Craig Moore, Bob Malcolm and Charlie Miller. Tommy Oar, Michael Zullo and Adam Sarota were bought by Dutch club FC Utrecht and striker Sergio van Dijk went to Adelaide United. Postecoglou, who asked to be judged a year from the time he took over, proved the critics wrong by winning and playing an entertaining brand of football. The Roar's possession based style of play under Postecoglou earned them the nickname "Roarcelona".
The 4–0 win against Adelaide United in round 13 was highly praised in the media as some of the best football the A-League has ever seen. Postecoglou led the Roar to the Premiership and Championship in the 2010–11 season, winning the Grand Final 4–2 on penalties against the Central Coast Mariners in front of 52,168 people at Lang Park. The Roar only lost one game all season and went on a 36-game unbeaten run, which broke the previous Australian football record. On 18 March 2011, he signed a two-year extension with the club keeping him until the 2013–14 season.
Postecoglou's side continued their winning streak in the 2011–12 season and now hold the all-time Australian football code record for longest undefeated sporting streak of 36 games, surpassing rugby league side Eastern Suburbs' record set 74 years ago. Postecoglou is managed by sports management company Football Focus International. In the 2011–12 season, Brisbane Roar became the first team to win back-to-back A-League championships and Postecoglou became the most successful Australian domestic football (soccer) coach, with four national titles.
On 24 April 2012, Postecoglou announced his resignation as head coach of Brisbane Roar. Postecoglou left the Roar after two-and-a-half years, during which he led the club to back-to-back A-League championships, a premiership and consecutive qualification for the AFC Champions League.
On 26 April 2012, it was announced that he had signed a three-year contract with A-League club Melbourne Victory as head coach. Postecoglou started rebuilding the team by releasing Matthew Kemp, Grant Brebner, Rodrigo Vargas, Tom Pondeljak, Ante Čović, Carlos Hernández, Harry Kewell and Fabio Alves, with Jean Carlos Solórzano and Ubay Luzardo returned to their respective clubs after their loan deals had expired. Postecoglou rounded up his squad by signing Jonathan Bru, Guilherme Finkler, Adama Traoré, Marcos Flores, Mark Milligan, Theo Markelis, Sam Gallagher and Spase Dilevski.
Postecoglou's first game in charge of Melbourne Victory was the Round 1 clash against crosstown rivals Melbourne Heart, an encounter which the Victory lost 2–1. His first win came against Adelaide United in Round 4, with the Victory prevailing 2–1. The following year, Melbourne Victory made the A-League Preliminary Final after beating Perth Glory in an Elimination Final 2–1 at Docklands Stadium. Melbourne Victory then played in the Preliminary Final against Central Coast Mariners and lost 2–0.
Postecoglou was appointed head coach of Australia on 23 October 2013 on a five-year contract, replacing German Holger Osieck, who was sacked after successive 6–0 defeats to Brazil and France. Postecoglou was tasked with regenerating the Australian national team, which was deemed to have been too reliant on members of their Golden Generation of 2006, subsequently leading to a stagnation of results, culminating in successive 6–0 defeats to Brazil and France. In his first game as Australia's manager, a home friendly match against Costa Rica, Australia won 1–0, courtesy of a goal from Tim Cahill.
For the 2014 FIFA World Cup, Australia were drawn in Group B alongside holders Spain, 2010 runners-up Netherlands and Chile. Their first match was off to a lacklustre start, having conceded only a goal from Tim Cahill before losing to South America's Chile 3–1. Their second match against the Netherlands was a close one, but their efforts ended in a 3–2 loss, thus earning their early exit along with the Spanish team. Australian fans praised the team for their outstanding efforts in a tough group. In the end, Australia finished Group B with a third defeat to former world champions Spain 3–0. Australia's competitive World Cup performances in a difficult group lead to belief that a new Golden Generation was about to begin, although at that time nobody thought this would be a new Golden Generation.
Postecoglou coached Australia in 2015 AFC Asian Cup. Australia beat Kuwait (4–1) and Oman (4–0), but lost to South Korea (0–1) in the qualifying rounds, before beating China (2–0) in quarter-final and United Arab Emirates (2–0) in the semi-final. Australia then beat South Korea (2–1) in extra time to win in the final to win its first AFC Asian Cup.South Melbourne
National Soccer League Championship: 1984, 1990–91
National Soccer League Premiership: 1992–93
National Soccer League Southern Conference: 1984, 1985
NSL Cup: 1989–90
NSL Premiership: 1997–98
NSL Championship: 1997–98, 1998–99
Oceania Club Championship: 1999
A-League Premiership: 2010–11
A-League Championship: 2010–11, 2011–12
OFC U-17 Championship: 2001, 2003, 2005
OFC U-20 Championship: 2001, 2002, 2005
AFF U-19 Youth Championship: 2006
AFC Asian Cup: 2015
National Soccer League Coach of the Year: 1997–98
PFA Manager of the Year: 2010–11
A-League Coach of the Year: 2010–11
PFA Manager of the Decade: 2015
AFC Coach of the Year: 2015
With Brisbane Roar FCLongest undefeated streak in Australian sporting history: 36 games (2011–12)
As of 6 September 2017