The Islanders announced the signing Sunday, but they did not confirm the financial terms.
The 31-year-old Komarov had seven goals and 12 assists in 74 games last season for Toronto. For his career, he has 52 goals and 70 assists in 327 games over five seasons, all with Toronto.
He made the most headlines last season for being on the receiving end of a kiss on the cheek from Bruins agitator Brad Marchand in the playoffs.
Komarov will fill the agitator/penalty-killing role for the Islanders previously held by free-agent Nikolay Kulemin.
New York also reportedly re-signed defenseman Thomas Hickey to a four-year, $10 million deal.
Hickey is coming off a season in which he had a career-high 25 points in 69 games, finishing with five goals -- one shy of his career high -- and matching his best with 20 assists. He has 22 goals and 89 assists in 409 regular-season games, all with the Islanders.
The Associated Press contributed to this report.