General manager Ray Shero announced the news Thursday.
"This morning, Travis Zajac underwent successful surgery to repair a torn left pectoral muscle that was suffered last week during off-season training," he said. "The procedure was performed by the club's Chief Medical Officer, Dr. Jonathan L. Glashow. Zajac's expected recovery time is approximately four to six months."
Zajac, 32, had 14 goals and 31 assists this past season, his 11th with the team since it drafted him in 2004.