Mahovlich received the Red Tilson Trophy as the top player in the OHA for the 1956–57 season, in which he scored 52 goals in 49 games.

At the same time, Punch Imlach was hired to run the Leafs and soon became head coach and general manager.

At that time, the National Hockey League All-Star Game was played at the beginning of the season, and during a reception in Toronto attended by team executives in the days before the 1962 game, Chicago Black Hawks owner James D. Norris offered the Leafs $1 million for Mahovlich.

He believed he had an agreement with Leafs co-owner Harold Ballard and paid $1,000 as a deposit with the balance to be delivered by cheque the next morning.

The next day, the Leafs gave Mahovlich the money he had been asking for and told the Black Hawks that their apparent agreement the night before had been a misunderstanding.

"Mahovlich is a sensitive, easily-bruised individual," wrote Milt Dunnell in a page-one story in the Toronto Star.

Mahovlich was part of a six-player blockbuster transaction in which he was traded along with Pete Stemkowski and Garry Unger from the Maple Leafs to the Detroit Red Wings for Norm Ullman, Paul Henderson and Floyd Smith on March 4, 1968.

He had 19 goals and 17 assists in 50 games that season and was the leading goalscorer in Maple Leafs franchise history with 296 at the time of the deal.

In 1970–71, Red Wings general manager Sid Abel wanted to get rid of coach Ned Harkness and was overruled by team owner Bruce Norris.

On January 13, 1971, Mahovlich was traded to the Montreal Canadiens for Mickey Redmond, Guy Charron, and Bill Collins.

According to John Brophy, when a reporter asked Mahovlich what was wrong, he replied, "I don't know, but I seem to play a lot better with Howe and Delvecchio.

"[5] He attempted an NHL comeback with the Detroit Red Wings in 1979, but it was unsuccessful, and he formally retired on October 7, 1979.