It was launched as W5 on September 11, 1966, just after the demise of CBC Television's This Hour Has Seven Days, at a time when the CTV network was on the brink of bankruptcy.

He quit only a few weeks into the first season of W5, in a dispute with John W. H. Bassett, who owned the CTV network's biggest station, CFTO-TV in Toronto.

[2] In 1993–94, an in-depth report on New Zealand showed the results of a nation that had suffered the effects of a debt wall.

Author Linda McQuaig criticized the program saying: "It was just full of misinformation," saying that Malling distorted the situation in New Zealand by presenting what was really a short-term currency crisis as something else: national bankruptcy and the loss of credit.

With broadcast shifting to HD for the 2009–2010 season the program reverted to its traditional title W5 with a revised graphic treatment and a new theme that reflects its investigative nature and culminates in five notes representative of the five Ws of journalism.

W5 has produced such stories as a possible cure for multiple sclerosis ("The Liberation Treatment"), an investigation into fatal shootings by RCMP officers (nominated for a Michener Award), an investigation of abuses at the Nova Scotia Home for Colored Children ("The Throwaway Children"), an annual expose of used car dealer trickery, rampant corruption in Canada's immigration system, and personal stories of burn recovery from the Bali bombing.

For a period of time in the late 1970s and into the 1980s, the program's introductory theme music used part of "Fool's Overture", a song by the UK band Supertramp.

On October 24, 2009, CTV unveiled a new look for W5, introduced a new logo and began broadcasting for the very first time in high definition.

In February 2024, as part of cuts by Bell Media, it was announced that W5 would conclude as a regular television series, with its final episode airing in March 2024.

Its first production, Narco Jungle: The Death Train (a five-part report on the Darién Gap), began airing on the CTV National News on September 30, 2024.

[7][8] The feature led to widespread protests by Chinese Canadians, including Joseph Yu Kai Wong (later founder of the Yee Hong Centre for Geriatric Care).