Blair was raised and educated in Werribee, Victoria. He began a journalism cadetship in 1988 at the now-defunct Truth newspaper in Melbourne. He went on to become its editor, the youngest person ever to hold the position. In mid-2001, he began blogging at Blogspot. By 2004, Blair had attracted a significant following, the Sydney Morning Herald describing him as a "top dog among the new Australian digerati" who "some days draws more than 20,000 readers to his website." In 2006, his relocated blog, timblair.net, was voted second "Best Australian or New Zealand Weblog" in the 2006 Weblog Awards. Today, Blair's blog is located on the Daily Telegraph website.
In addition to running his blog, Blair is the opinion editor for the Sydney Daily Telegraph, where he also writes a weekly column. He was previously a news editor and regular columnist for the now-defunct The Bulletin. He has also worked as a journalist and senior editor at Time, Truth and Sports Illustrated, and has also written for Fox News. Blair has also appeared on 4BC, Radio National and the ABC programme Insiders.
Blair supports the Collingwood Football Club and lives in Surry Hills, New South Wales. He is married. In January 2008, Blair announced on his blog that he had abdominal cancer and wrote about his impending surgery (and encouragement from Tony Snow) in a newspaper column. The surgery was successful and Blair went into remission.
Blair is known for his conservative political views. He is critical of 'Islamofascism' and those he considers climate change alarmists and hypocrites. He has criticised the work of other journalists and bloggers, including Margo Kingston, and writers Elizabeth Farrelly, Mike Carlton, Terry Lane, Mark Lawson, Tracee Hutchison of The Age, and Robert Fisk. Politician Al Gore and cartoonist Michael Leunig are also regular targets. In contrast, Blair frequently quotes writers such as Mark Steyn, James Lileks and Andrew Bolt with approval.
Starting a few days after George W. Bush's visit to Baghdad during Thanksgiving 2003, Blair has documented and disproved claims that a roast turkey that Bush was photographed holding up was plastic. The roast turkey was real.
Some bloggers use the term "Blair's Law" to describe a theoretical alliance or shared empathy between far right groups, far left groups and extremist Islamists. In 2002, Blair described this supposed alliance as an "ongoing process by which the world's multiple idiocies are becoming one giant, useless force". The phrase has been adopted and embraced by several conservative and libertarian bloggers.
In 2007, Media Watch, an Australian Broadcasting Corporation TV program which Blair has often criticised, stated that The Daily Telegraph, other newspapers and Blair failed to censor racist comments on their websites. Blair and the Telegraph reported that Media Watch had themselves failed to censor antisemitic comments at their own website, and that their story relied on "unacknowledged assistance" from "Muslim Village, [a website which] is guilty itself of publishing offensive comments". The ABC later launched an internal inquiry into Media Watch's dealings with Muslim Village.
In March 2009, Pure Poison, a blog hosted by online media site Crikey, alleged that Blair "comments under a pseudonym on his blog and various other blogs" and was "unprofessional in his conduct as a journalist". Both Pure Poison and Crikey issued a partial retraction a few days later. In April 2010, Pure Poison and Crikey fully retracted their report and apologised, after Blair commenced legal action. Blair subsequently accepted a confidential settlement. This legal action drew claims of hypocrisy from some quarters, based on Blair once claiming that "journalists suing journalists" was "graceless and weird". (None of the Pure Poison bloggers were journalists.)
In August 2010, Crikey amended an online article, written by Guy Rundle, that "misrepresented the views of Tim Blair and Andrew Bolt", admitting that "references to them were offensive and indefensible."
On 17 June 2014 Tim Blair published a blog post titled 'Crown Our Crazy Queen', which asked his readers to vote for 'Who is Australia’s craziest left-wing frightbat?', out of a choice of various Australian feminist columnists, writers and activists. The 'winner' was Vanessa Badham, a columnist for The Guardian.  This episode triggered a storm of controversy, including responses from the 'frightbats' Blair had nominated.     Blair responded to the controversy by stating that "When you describe hysterical crazy people as crazy and hysterical, it creates hysterical craziness." 
- "Richard Fidler interviews Tim Blair, ABC Radio, 28 July 2006"
- "Shooting for top dog in cyber town", Brigid Delaney, The Sydney Morning Herald, 6 October 2004
- The 2006 Weblog Awards — Best Australia or New Zealand Blog
- "Employment News", TimBlair.net, 20 November 2006
- "Just for the record", TimBlair.net, 2 September 2007
- Tim Blair (14 January 2008). "A Visit to the Infirmary". TimBlair.net.
- Tim Blair (19 January 2008). "Grit your teeth and grab that devil by the throat". The Daily Telegraph.
- Tim Blair (5 February 2008). "Recovery Update". TimBlair.net.
- Tim Blair (7 December 2003). "The Guardian's Plastic Turkey". TimBlair.Spleenville.com.
- Tim Blair (31 August 2006). "Turkey Roll". TimBlair.net.
- Tim Blair (17 March 2007). "Rudd and the turkey role". The Daily Telegraph.
- Tim Blair (blog post) (11 May 2011). "As We All Know". The Daily Telegraph.
- "Corrections". The New York Times. 11 July 2004.
- Post by Tim Blair (at an earlier blog), 23 May 2002
- "Ted Rall, David Duke, Robert Fisk, Lyndon LaRouche, al-Ahram, Hitler, Noam Chomsky, Blair's Law, the Arab News, and Me", Frank Portman, Blogs of War, 15 May 2002
- "Why I am not Celebrating Today's News from Austria", Ben Ze'ev, Six Days blog, 21 February 2006
- "It's Not Just A Good Idea, It's Blair's Law", Ed Driscoll, 4 September 2006
- "Idiots of a Feather...", J. F. Beck, RWDB blog, 12 December 2006
- "Have Your Spray", Media Watch, 18 June 2007
- "Prejudice Expressed", Tim Blair, timblair.net, 19 June 2007
- "Media Watch fails racism test", The Daily Telegraph, 25 June 2007
- "Friends of the ABC", Tim Blair, timblair.net, 25 June 2007
- "Antoinette Helped", Tim Blair, timblair.net, 27 June 2007
- "Media Watch's jihadi sources", Richard Kerbaj, The Australian, 12 July 2007
- "Crikey Apologises to Tim Blair". Crikey. 12 April 2010.
- Tim Blair (2 March 2009). "Journalism in the Age of Crikey". Daily Telegraph blogs.
- Sean Nicholls and Leesha McKenny (13 April 2010). "Blair bitch project". Sydney Morning Herald.
- "Blogger's weird decision to sue" Sydney Morning Herald, 1 April 2010
- Tim Blair (28 August 2010). "Crikey Regrets". Daily Telegraph blogs.
- Tim Blair (17 June 2014). "'Crown Our Crazy Queen'". Daily Telegraph blogs.
- Vanessa Badham (2 July 2014). "When they call us 'frightbats', they make us fair game". The Guardian blogs.
- Jenna Price (18 June 2014). "Be very worried, Tim Blair – we are all frightbats now". The Conversation blogs.
- Elizabeth Farrelly (26 June 2014). "Feminist frightbat campaign just the Blair Witch project". Sydney Morning Herald blogs.
- Georgina Dent (18 June 2014). "What is a 'frightbat'? The search for Australia's ‘most unhinged hysteric’". Women's Agenda blogs.
- Tim Blair (19 June 2014). "Frightbattery Fury". Daily Telegraph blogs.