Hadfield is of northern English and southern Scottish descent. He is a devoted fan of the Toronto Maple Leafs and wore a Leafs jersey under his spacesuit during his Soyuz TMA-07M reentry in May 2013. After the 2012 NHL Lockout ended, Hadfield tweeted a photo of himself holding a Maple Leafs logo, and stated he was "ready to cheer [his team] on from orbit". He sang the Canadian National Anthem during the Toronto Maple Leafs and Montreal Canadiens game on January 18, 2014 at the Air Canada Centre in Toronto.
In June 2013, one month after completing his third trip to space, Hadfield announced his retirement from the Canadian Space Agency, effective July 3, 2013. Hadfield stated that after living primarily in the United States since the 1980s for his career, he would be moving back to Canada, "making good on a promise I made my wife nearly 30 years ago—that yes, eventually, we would be moving back to Canada." He noted that he plans to pursue private interests outside government there.
Hadfield has a social media presence, with over 2,400,000 Twitter followers as of August 2019. He created one of the top Reddit AMA threads of all time on February 17, 2013. He is also on Facebook, Tumblr, and YouTube. His exchanges with William Shatner and other Star Trek actors have received media coverage. Hadfield has been described by Forbes as "perhaps the most social media savvy astronaut ever to leave Earth".
His collaboration with Ed Robertson of the Barenaked Ladies and the Wexford Gleeks, Is Somebody Singing?—sometimes shortened I.S.S.—was aired on the CBC Radio program Q and released by CBC Music online on February 8, 2013. Hadfield sang Is Somebody Singing along with singers across Canada for the national Music Monday program. Hadfield has been credited musically on his brother Dave Hadfield's albums. He also has performed with his brother the "Canada Song", which was released on YouTube on Canada Day, 2014.
On May 12, 2013, after handing over command of the ISS, but before returning home, Hadfield released a music video recorded on the ISS of a modified rendition of "Space Oddity" by David Bowie. As of January 2020, the video has over 45 million views on YouTube. The performance was the subject of a piece by Glenn Fleishman in The Economist on May 22, 2013, analysing the legal implications of publicly performing a copyrighted work of music while in earth orbit.
In October 2013 Hadfield was interviewed by Maclean's magazine and appeared on its cover wearing face make-up to "replicate Bowie's famed image from the cover of his Aladdin Sane album." Hadfield wrote an article for the December 2013 edition of Wired magazine in which he reflects on his time spent on the International Space Station.
On October 8, 2013 the University of Waterloo announced that Hadfield will join the university as a professor for a three-year term beginning in the Fall of 2014. Hadfield's work is expected to involve instructing and advising roles in aviation programs offered by the Faculty of Environment and Faculty of Science, as well as assisting in ongoing research regarding the health of astronauts with the Faculty of Applied Health Sciences.
Hadfield's 2013 autobiography, An Astronaut's Guide to Life on Earth: What Going to Space Taught Me About Ingenuity, Determination, and Being Prepared for Anything deals with his professional life and work, and with numerous examples from the lead-up to his command of Expedition 35. The book was a New York Times bestseller and was also the bestselling book in Canada on a Canadian subject.