Prime Minister Justin Trudeau of Canada announced on Wednesday that he and his wife, Sophie Grégoire Trudeau, had separated after 18 years of marriage.

The Trudeaus, who have three children, have “signed a legal separation agreement,” according to a statement released by the prime minister’s office.

“As always, we remain a close family with deep love and respect for each other and for everything we have built and will continue to build. For the well-being of our children, we ask that you respect our privacy and their privacy,” Mr. Trudeau said in a post on Instagram.

He added that they had decided to separate “after many meaningful and difficult conversations.”

Mr. Trudeau’s wife and children have played a prominent role in his political career, often accompanying him on trips overseas after he was elected prime minister in 2015. Their children are Xavier, 15, Ella-Grace, 14, and Hadrien, 9.

His young children have helped craft an image of Mr. Trudeau, now 51, as a youthful, vigorous leader. His wife, 48, is a former television presenter and helped burnish his image further with a touch of glamour.

The prime minister’s office said that the couple “are focused on raising their kids in a safe, loving and collaborative environment.” It added that they “will be a constant presence in their children’s lives” and that the family planned to vacation together next week.

“Canadians can expect to often see the family together,” the office said.

The couple met in Montreal in 2002 and were married three years later, after Mr. Trudeau, who had spent years teaching in Vancouver, returned to Montreal.

Nelson Wiseman, a professor emeritus of political science at the University of Toronto, said that while Ms. Grégoire Trudeau prominently accompanied her husband at public events after he became prime minister, her appearances had more recently decreased notably.

Even though the role of family man was an integral part of Mr. Trudeau’s carefully crafted image, Mr. Wiseman said he foresaw no political fallout from the separation.

“Canadian voters don’t care about that,” he said. “Once upon a time, they did. But the culture and times have changed.”

Mr. Wiseman pointed out that even Mr. Trudeau’s father, Pierre, did not suffer politically after he separated in 1977 from his wife, Margaret, the current prime minister’s mother. Pierre Trudeau served as prime minister nearly continuously from 1968 to 1984.

The announcement came as Mr. Trudeau overhauled his cabinet last week, shuffling ministers in key portfolios to inject what he called “fresh energy” into the team. Political analysts say it’s an attempt to get his party in fighting form for the next scheduled election in 2025, with recent polls showing that Mr. Trudeau’s Liberal Party is lagging behind the Conservatives.