Hockey Canada said Thursday it contacted the Maple Leafs and it was agreed it was best for Tavares to return to Toronto for further evaluation of his oblique.
"We are disappointed that John will not be able to participate as a member of Team Canada," Hockey Canada official Jason Botterill said in a statement. "We know John was excited about the opportunity to wear the Maple Leaf once again, and we were excited to have John as a member of our team and to welcome his many years of NHL and international experience."
Canada opened play in the world championships on Friday with a 3-1 loss to Finland. The event runs through May 26.
Tavares, 28, has played on three previous world championship teams for Team Canada. He won a gold medal at the 2014 Olympics, where he injured his left knee and missed the rest of that NHL season.
He had a career-high 47 goals and 41 assists while playing all 82 games this season, his first with the Maple Leafs after signing with Toronto as a free agent.
He also played all 82 games in 2017-18, his final season with the New York Islanders.
The six-time All-Star has 272 goals and 349 assists in 10 NHL seasons.
The Associated Press contributed to this report.