Hird participated in rugby league, ballet and soccer in his youth. He played for the Ainslie Football Club in the ACTAFL and in June 1990, at the age of 17, he was a member of the league’s senior representative team in a match against the Victorian Football Association. He was recruited to the AFL by Essendon from the 1990 AFL Draft; due to a serious hip injury along with other injuries in his junior football career, he was not selected until pick number 79, Essendon’s seventh pick and one of the last in the draft.

Due to injury Hird missed out on playing for most of 1991, his first season with the club. At the end of the season, a vote was held on whether to delist him. The majority (4–2) voted in favour of Hird being delisted, although coach Kevin Sheedy voted to keep him. Eventually Hird remained with the club. He made his senior debut against St Kilda in 1992 at Waverley Park, as a late replacement for former captain Terry Daniher. Hird spent most of the season in the Essendon Reserves which, under Denis Pagan, won the premiership that season. He achieved regular selection in the Essendon senior team during the 1993 season. In that season he was a member of what was referred to as the “Baby Bombers”, a group of young players (most notably including Hird, Mark Mercuri, Gavin Wanganeen, Dustin Fletcher, Ricky Olarenshaw, David Calthorpe, Paul Hills and Joe Misiti) that played a key role in the side winning the premiership that year. In 1994, Hird won the first of three consecutive best and fairests, culminating in his 1996 season, when he won the Brownlow Medal.

Hird jointly won the Brownlow Medal with Michael Voss in 1996, the award for the fairest and best player in the Australian Football League. After his retirement, Hird stated that being a member of the “Brownlow Club” was a privilege.

A series of injuries restricted Hird’s appearances during the remainder of the 1990s. He played only seven games in 1997 and although he was named captain in 1998 (a position he held until the end of 2005), he was restricted to thirteen games that year. An even worse year followed in 1999, when stress fractures in his foot kept him to only two games.

In 1997, the Essendon Football Club named the then-triple best and fairest winner in its Team of the Century on the half-forward flank.

Hird married Tania Poynton on 11 October 1997 and they have four children, a daughter and three sons.

Hird completed a bachelor’s degree in civil engineering in 1998 and worked in that capacity as a consultant on the CityLink project. He has also spent time working for a stockbroking firm and is an active partner in Gemba – a sports marketing and media consultancy firm based in Melbourne.

Both Hird and the Essendon Football Club experienced a more successful year in 2000. Injury free, he received numerous honours, including selection in the All-Australian team, and the Norm Smith Medal as best on ground in the AFL Grand Final. The Essendon team also won the Ansett Cup pre-season competition, and the regular season premiership. The team only lost one game – against the Western Bulldogs – in the entire calendar year.

2002 then saw Hird’s worst injury, an horrific facial injury sustained in a match against Fremantle when he collided with teammate Mark McVeigh’s knee, fracturing several bones; Hird was in hospital for a week and missed several weeks of the season.

In 2002, the Essendon Football Club conducted a fan-voted promotion to find the “Champions of Essendon”. Hird was eventually named as the number three player on the all-time list of Essendon players.

In 2003, despite again missing eight games through various injuries, Hird tied in the Essendon Best and Fairest with Scott Lucas. He also narrowly missed out on a second Brownlow Medal, finishing three votes behind the joint winners Mark Ricciuto, Nathan Buckley and Adam Goodes. He again gained a place in the 2003 All-Australian team.

On 27 September 2005, Hird handed the captaincy to Matthew Lloyd following the side’s disappointing 2005 season in which it missed the finals for the first time since 1997.

One of Hird’s more memorable performances was in his Round 3, 2004 game against West Coast. Up until three-quarter time, Hird had 19 disposals and one goal; in the final quarter, he managed 15 disposals and two goals. Hird did not receive any Brownlow Medal votes from the umpires for his 34 disposals. Hird’s winning goal was the focus of a popular instalment of the Toyota Memorable Moments advertising campaign, and the hug is captured in Jamie Cooper’s painting the Game That Made Australia, commissioned by the AFL in 2008 to celebrate the 150th anniversary of the sport.

Before season 2008, the Archer-Hird Medal was created honouring Hird and former North Melbourne Football Club player Glenn Archer. Since 2008 the medal has been awarded to the player showing the most determination, courage and skill in matches between the Kangaroos and the Bombers.

Immediately after Hird retired from playing football there was much speculation as to whether he would be interested in a coaching role at a club in the AFL, but primarily at Essendon. After initially dodging questions about his future, Hird stated in August 2010 that “There’s something in me, deep in my heart, that says at some point I want to coach Essendon”. These words came as a surprise to many, including former premiership teammate Matthew Lloyd who said that Hird had “changed his whole persona in regards to how he’s answering his questions… Just in regards to saying, ‘I’ll coach one day. I want to coach Essendon one day’. Even those type of words, I haven’t heard before.” These comments by Hird, considered to be Essendon’s “favourite son”, furthered speculation towards the future of then-Essendon coach Matthew Knights. A rumour emerged following these comments suggesting that Hird was part of an unofficial agreement with the Essendon board to replace Matthew Knights for the 2011 AFL Season. However, two days after Hird’s initial comments, he announced that he had changed his mind due to the intense division and speculation over Matthew Knights’s future following Hird’s initial comments. Hird stated that he was ruling himself out of coaching Essendon for at least three years.

On 28 September 2010, the rumours were confirmed when Essendon’s chief executive officer, Ian Robson, and chairman, David Evans, announced at an official press conference that Hird would be the next senior coach of the Essendon Football Club on a four-year contract.

The 2013 season was initially a good one for Hird and the football club, during which the team was second on the AFL ladder with a 13–3 win-loss record after 17 rounds. However, internal pressure on the club finally took its toll on the players and coach when the AFL banned Essendon from participating in the 2013 finals series. The club on-field performances fell away and lost five of their last six games. In August 2013, he was suspended from coaching for 12 months when he was charged by the AFL with conduct prejudicing the game in relation to his role in the Essendon Football Club supplements controversy.

In April 2013, Hird, as coach, was accused of being personally injected with supplements in 2011 and 2012 that would be deemed performance enhancing if he were a player. Essendon players from 2011 and 2012 were also accused of ingesting performance enhancing supplements. As head coach, Hird was subsequently implicated.

Following months of rumours and investigations, on 13 August 2013, Hird, along with the Essendon Football Club, senior assistant coach Mark Thompson, football manager Danny Corcoran and club doctor Bruce Reid, was charged by the AFL with bringing the game into disrepute in relation to the poor governance of the supplements program at the club in 2011 and 2012. The club was given 14 days to consider the charges and faced an AFL Commission hearing on 26 August 2013.

On 27 August 2013, following much negotiation, Hird accepted charges that he had brought the game into disrepute and abandoned possible Supreme Court action against the AFL and its chief executive, Andrew Demetriou. He maintained that he did little wrong, but said he should have known more about the club’s supplements program. He was banned from working at any AFL club in any capacity for twelve months commencing from 25 August 2013. Hird was allowed to attend Essendon matches as a spectator during this period. However, despite not being allowed to pay him for working as a coach during 2014, the club paid Hird $1 million in advance for 2014 in December 2013.

A media report on 3 October 2013 said that Hird denied pleading guilty for a reduced charge as alleged by Demetriou. Hird’s lawyer, Steven Amendola, asserted that the AFL withdrew all charges against Hird under the deeds of settlement that he and the club signed with the AFL. At the time of the media report, Hird was considering legal action against both the AFL and Demetriou.

Banned from coaching in 2014, Hird spent several months living in France attending an exclusive business school, INSEAD, near Paris. He returned to the club following the 2014 season. Shortly after returning from his suspension, on 2 October 2014, it was reported that Hird was to be sacked by Essendon due to his determination to lodge an appeal against the Federal Court decision handed down the previous month when the club had chosen not to.

On 18 August 2015, following a 112-point loss to Adelaide and a dismal season overall for the Essendon Football Club, by which time they had a 5–14 win-loss record and were fifteenth on the AFL ladder, Hird resigned as senior coach.

Essendon chairman Paul Little said that Hird would be wanted as the senior coach once his suspension was served and that he had been offered a two-year extension from 2015, which would have seen him coaching until the end of the 2016 season. However, Hird resigned after round 20 in August 2015, near the end of the season, with the team near the bottom of the ladder.

On 5 January 2017, Hird was taken to a private hospital following a drug overdose and was subsequently transferred to a specialist mental health care facility for further care and treatment.

On 28 November 2018, James Hird was hit by a car when cycling in Richmond.