In addition to job cuts sprinkled across the country, the newspaper publisher is closing down eight community newspapers and its 24 Hours free daily papers in Ottawa, Calgary and Edmonton.
The company said the plan is expected to yield annual savings of approximately $55 million.
"We don't have a choice, because if we don't do this we won't survive," said Martin Tremblay, a spokesman for Sun Media's parent company, Montreal-based Quebecor Inc. (TSX:QBR.B)
"If we want to succeed in the future, we're going to have to invest more money in digital and the website and trying to bring in new, young readers."
A memo circulated to staff said the cuts represented about eight per cent of the company's workforce.
"Our vision is to continue to be the leading news media provider in Canada while being the most profitable in the industry," the note from chief operating office Julie Tremblay said.
"This means that we will continue to focus on great journalism, hard hitting information that reports on issues that matter most to people. It also means that we will continue to partner with our advertisers to offer them innovative solutions in reaching customers and furthering success."
The cuts come on the heels of 500 job cuts at Sun Media newspapers last November, including the closure of two production facilities in Ottawa and Kingston.
The layoffs Tuesday included Stephen Ripley, the editor-in-chief of the Winnipeg Sun, who will be replaced by the paper's managing editor Mark Hamm, Quebecor said.
Sun Media said it made the decision to close the three 24 Hours newspapers because it wants to focus on a single urban newspaper in each market, except Montreal and Toronto, where it says large transit systems warrant publishing the free papers.
The company will also continue to publish 24 Hours in Vancouver, where Sun Media doesn't have another daily newspaper.
In addition to the 24 Hours papers, Sun Media is closing eight newspapers in smaller communities in several provinces including three in Quebec.
The closures include Le Magazine Saint-Lambert, Le Progres de Bellechasse and L'Action Regionale in Monteregie, Que., the Lindsay Daily Post and the Midland Free Press in Ontario, the Meadow Lake Progress in Saskatchewan and the Lac du Bonnet Leader and the Beausejour Review in Manitoba.
Unions representing workers at Sun Media papers raised concerns about the impact the cuts will have on the quality and availability of local news.
"Local newspapers are the only ones that are watching town hall, watching what developers are doing," said Martin O'Hanlon, director of the Communications Workers of America Canada.
Paul Morse, president of the Southern Ontario News Media Guild, which represents workers at 13 Sun Media papers in Ontario, said 15 of the union's members have lost their jobs.
Five are at the Toronto Sun, five at the St. Catharines Standard, three at the Brantford Expositor, one at the London Free Press and one at the Ottawa Sun, Morse said.
"One of the reasons that we enjoy the freedoms that we have in this country and the standard of life that we have in this country is because we have a press that operates independently and professionally," Morse said.
"If we lose that, it'll have a major impact on our lives as we know it. It's a very, very slippery slope."
A reporter at the North Bay Nugget and one at the Sault Star are also among the layoffs, O'Hanlon said.
"There's almost no one left to cut," he said.
"The staffing levels in the newsrooms are so low that people right now have a hard time going on holiday, and coping with the work is almost impossible. Even cutting one reporter in the newsroom is devastating."
Declining advertising revenues have hit the newspaper industry hard.
Newspaper publishers across the country have moved to cut costs as rising digital advertising revenue has failed to make up the losses from traditional print advertising.
Quebecor warned earlier this year that it would not rule out further cost-cutting efforts to address the drop facing its newspaper business.
The company saw its first-quarter net profits fall to $35.6 million in May, down from $71.4 million the previous year.
Quebecor also announced Tuesday that Wendy Metcalfe, editor-in-chief of the St. Catharines Standard, will become the new editor-in-chief of the Toronto Sun.
She replaces James Wallace, who stepped down on Monday.
Sun Media has 36 paid-circulation daily newspapers and three free dailies as well as almost 200 community newspapers, shopping guides and other specialty publications.