Mansbridge was born on July 6, 1948, in London, England. He and his siblings Paul and Wendy were the children of Stanley Harry Mansbridge, D.F.C. (1918–2005), an RAF Wing Commander who worked as a civil servant in England, Malaya, and Canada; and Brenda Louise Mansbridge (née Harris-Jones, died 2008). His father received a D.F.C. for his service as a navigator aboard an Avro Lancaster bomber during World War II. After moving to Ottawa, Ontario, Peter attended high school at the Glebe Collegiate Institute, but dropped out before graduating. He served in the Royal Canadian Navy in 1966 and 1967.
Mansbridge worked as a ticket agent for Transair at Churchill Airport in Churchill, Manitoba. In 1968, Mansbridge was discovered by Gaston Charpentier, a station manager for the local Canadian Broadcasting Corporation (CBC) radio station CHFC, when he heard Mansbridge making a flight announcement. Charpentier hired the 19-year-old Mansbridge as the host of CHFC's late night music program. In 1971, Mansbridge moved to Winnipeg to continue as a reporter for the CBW radio station and in the next year, he joined CBWT-TV as a reporter.
In 1975, Mansbridge became a reporter in Saskatchewan for the CBC's flagship evening news program The National. In 1976, he relocated to Ottawa to become parliamentary correspondent. Following a decade of political coverage, Mansbridge had become a substitute anchor for Knowlton Nash and in 1988, CBS offered him a job as a co-anchor for a morning show. To keep Mansbridge in Canada, Nash retired from his anchoring duties at the CBC.
Mansbridge was also the announcer of CBC News' This Week In Parliament (1981–1993), which was hosted by colleague Don Newman; Mansbridge provided the voice-over for the opening, intro, and ending of the program.
On May 1, 1988, Mansbridge debuted as the sole anchor of The National and later served as co-anchor for CBC Prime Time News from November 1992 to Fall 1995. During his tenure as anchor, he has covered Canadian news stories including federal elections, party leadership conventions, the Meech Lake Accord negotiations, the Charlottetown Accord and its referendum, the 1995 Quebec referendum, floods in Manitoba in 1997, ice storms in Ontario and Quebec in 1998, the six days in September 2000 that marked the death and state funeral of Pierre Trudeau, the 2003 blackout across much of Eastern North America and the death and state funeral of Jack Layton. His coverage of the blackout was notable because the normally clean-shaven Mansbridge had grown a beard during his summer hiatus (as he did every summer), and the news of the blackout broke with no time for him to shave. Thus, Canadian viewers saw a bearded Peter Mansbridge reporting on the events of that day.
He has also anchored coverage of many world events, both in the studio and on the scene. In the studio, he anchored coverage of the Gulf War, the War in Kosovo, the September 11 attacks and the 2014 Parliament Hill shootings. He was on the air live when the 2003 invasion of Iraq began and anchored coverage of it. On the scene, he anchored coverage of the fall of the Berlin Wall, the funerals of Diana, Princess of Wales and Pope John Paul II, numerous royal, papal, and US presidential visits to Canada, numerous Olympic Games, and the inauguration of US President Barack Obama. He reported extensively from Normandy both 50 and then 60 years after D-Day and from the United Kingdom and the Netherlands for the fiftieth anniversary of V-E Day. He also reported from the Netherlands for the sixtieth anniversary of V-E Day.
In 1999, he launched a new program, Mansbridge One on One, in which he interviews newsmakers.
With the retirement of Lloyd Robertson of CTV National News on September 1, 2011, Mansbridge became the longest-serving active anchor among the big three networks in Canada, as Dawna Friesen had taken over as anchor at Global National only in 2010. Lisa LaFlamme taking over for Robertson also meant that Mansbridge is the only male chief anchor among the big three English networks in Canada (Mansbridge, LaFlamme, and Friesen).
In 2014 Mansbridge faced criticism for accepting speaking fees. Mansbridge defended himself saying he gave about 20 speeches each year, about half of them unpaid, and that he often donates part of the money to charity. However, he'd recently made a paid speech for a lobby group, the Canadian Association of Petroleum Producers’ (CAPP) Investment Symposium, who promoting the pro-oil-sands-development side of the debate. Media critics felt accepting payment from an agency actively trying to influence public policy, even if it was only as a speaking fee, could be a conflict of interest. Mansbridge was the second CBC employee discovered to be accepting money from outside agencies for speaking fees. Rex Murphy of CBC's Cross Country Check-up was the first. CBC president Hubert Lacroix defended the practice stating that the CBC was aware of the speaking engagements and payments, having pre-vetted them for any potential conflict of interest. Nevertheless, the CBC reviewed its policies following the controversy.
In recent years, Mansbridge has cut back his schedule mostly to Monday through Thursday. While he is billed as anchoring The National throughout the week, Sunday anchor Wendy Mesley has anchored most Fridays as well. Mansbridge stepped down from anchoring The National on July 1, 2017.
From October to December 2017, Mansbridge will undertake a 17-stop cross-Canada storytelling tour.
Mansbridge has been married three times. His previous marriage to CBC colleague Wendy Mesley (January 6, 1989 – 1992) became regular tabloid fodder in Frank magazine as their marriage ended. He has been married to Canadian actress Cynthia Dale since November 14, 1998, and they have a son, William, born in 1999. Mansbridge has two daughters from a first marriage to Parm Dhillon, which ended in 1975. He lives in Stratford, Ontario with his family, and also has a summer cottage in the Gatineau Hills.
Among his hobbies, Mansbridge collects small mementos from his travels around the world, including rocks, soil and other “sentimental” items from various prominent historical places. He kept pebbles from a visit to the Battle of Dieppe site in France, dirt from Vimy Ridge, and sand from the beaches at Normandy, as well as pieces of the Berlin Wall and the Great Wall of China. A silver bracelet was bought on his trip to South Africa for Nelson Mandela's funeral, which is engraved only with the numerals “46664” — Mandela’s prisoner number on Robben Island.
Mansbridge is also an avid and longtime fan of the Winnipeg Jets, having attended the signing of Bobby Hull in 1972 while working as a reporter for CBWT. Mansbridge's public support for the Jets – including use of his Twitter account – is often seen as a humorous contrast to his balanced reporting style. To underline this image, Mansbridge is also known to occasionally make jokes at the expense of the Toronto Maple Leafs. Nonetheless, he continues to support his childhood Maple Leafs in a secondary capacity.
Mansbridge had a voice cameo in the 2016 Walt Disney Animation Studios film Zootopia as "Peter Moosebridge," an anthropomorphic moose news anchor.
Mansbridge has won several honours throughout his career, including 12 Gemini awards. In 2008, he was made an Officer of the Order of Canada, the second grade of nation's second highest civilian honour. In that capacity, the Queen Elizabeth II Diamond Jubilee Medal was also conferred upon him in 2012.
Peter Mansbridge has received a number of honorary degrees; these include: