Haddin's family moved to Queanbeyan in 1989 when he was 12 and he played for the Queanbeyan District Cricket Club Juniors to the age of 15 before joining the Australian National University Grade Cricket Club, representing 1st grade at age 16. Haddin was selected in the first ever Mercantile Mutual Cup season of 1997–98 for the ACT Comets, with whom he began his professional cricketing career. In the 1999–2000 season, he began playing for the New South Wales Blues to pursue further cricketing opportunities. Since then, he has produced several memorable batting innings, including a top score of 133 against Victoria. Haddin was signed by Chennai Super Kings in the 2010 IPL. In the 2011 Indian Premier League season, Haddin was contracted by Kolkata Knight Riders for US$325,000.

On 26 September 2012, Haddin scored a century in a Sheffield Shield match against Tasmania at the Bankstown Oval, his first since his century in the first Ashes test against England in November 2010.

In November 2015 Haddin made his return to the ACT Comets for the first time since the 1998–99 season, where he played a Futures League match and made a century in his first innings, ending on 104 off 100 balls, making him only the sixth player to score a century on debut.

Haddin played for Islamabad United in the Pakistan Super League held in the UAE in February 2016. He was retained by United's team management for 2nd season.

In September 2003, Haddin replaced Simon Katich as captain of New South Wales, while Katich was on international duty, and he since been acting-captain on numerous occasions. He has also captained Australia A. For most of his career Haddin was Australia A wicketkeeper but was drafted into the full squad as back-up wicketkeeper in case Adam Gilchrist was injured or rested. He made his international debut in a one-day international on 30 January 2001 against Zimbabwe in Hobart. He made one stumping and made 13 runs. He was demoted from second choice wicket keeper for Australia in 2001 by Wade Seccombe and later Ryan Campbell, but reclaimed this position in late 2004. He was called up as part of Australia's 2005 Ashes squad but was not used throughout the series.

On 18 September 2006, playing against West Indies at Kuala Lumpur in the DLF Cup, Haddin and Australian captain Mike Hussey put on 165, which at th