White, 55, was a steady hand on the tiller in recent years as the organization endured an often rocky transformation from non-profit co-operative to for-profit company in an era of dwindling media revenues.
"It just felt like a good time to do it," White said Monday of his decision to step down.
"Everybody should at some point admit that it's a good time for somebody else to bring in new ideas."
White, who recently completed an executive MBA program, said he has a new job but did not disclose details. His resignation is effective March 21.
In many ways, White personified the company's heart and soul: self-effacing but demanding attention, all the while wedded to uncompromising standards of accuracy, speed and fairness, regardless of platform.
"There is no other news organization in this country that is more devoted than CP to the daily duty — and we all see it as a duty — of producing an objective news report that keeps Canadians informed," he said in a memo to staff.
"We have a uniquely single-minded devotion to the story, rather than the byline."
Malcolm Kirk, president of The Canadian Press, said he was saddened that White, a "newsman through and through," was leaving.
"Scott has been an inspirational leader — an outstanding boss and a huge believer in quality journalism," Kirk said.
"It's going to be tremendously difficult to fill his shoes."
At the same time, Kirk said, White leaves the organization in "terrific shape."
With his frank talk and salty language, White could be a tough boss, said Heather Boyd, a longtime CP staffer, who currently serves as the company's Edmonton-based Western Canada bureau chief.
"It's difficult to imagine anyone being more creative or indefatigable than Scott White," Boyd said.
"His conversations were often peppered with his favourite expletive, but he inspired intense loyalty from members of his team."
Monday's announcement was greeted with shock and disappointment by many of the agency's employees, both past and present.
"Stunned," tweeted Allison Jones, an eight-year veteran of CP's Toronto newsroom.
White held "one of the most important jobs" in Canadian journalism, said Les Perreaux, a former CP reporter who now works with the Globe and Mail.
"Most of you never heard of him," Perreaux tweeted. "This says everything about him."
CP, which is owned by a consortium comprising the Globe, Toronto Star parent Torstar Corp. and Square Victoria Communications Group, provides print, audio, photographic and video services to newspaper, radio, television and online clients across the country.
Hired in May 1979 as a 20-year-old straight out of journalism school, White — who hailed from the southwestern Ontario town of Chatham — played a wide variety of roles in the company's newsrooms over his 35 years at CP.
He served as a political reporter in the Ontario legislature, sports editor, Washington correspondent, Vancouver bureau chief and head of the pictures department, before assuming the top editorial job more than 15 years ago.
Ivor Shapiro, chairman of the School of Journalism at Ryerson University, called Scott's departure "the end of an era."
"Scott is one of those rare people in the news business, or any business, who are universally respected," Shapiro said.
A Harley-Davidson enthusiast with a passion for baseball and Batman, White was a constant presence in and around the newsroom, preferring a comfortable pair of jeans to the suit-and-tie look his role often demanded.
Those who sat across from him in morning meetings knew the news — and CP's reporting of it — could elicit an unbridled belly laugh as easily as it could a torrent of profanity when the work didn't pass muster.
Regardless of mood, however, his passion for the news business never seemed to waver.
"The thing that's most surprising is that 35 years have gone by in the blink of an eye," White said.
"I still find the place as exciting as I ever did."