The extension will include a team option in the third year, sources told the Athletic's Shams Charania.
Winslow was eligible for an extension being a member of the 2015 draft class. Had he not come to terms with Miami prior to Monday's deadline, he would've entered restricted free agency on July 1.
Due to the poison pill provision in his extension, it's extremely unlikely that the Heat will be able to trade the 22-year-old forward at some point this upcoming season, with the franchise still heavily linked to Minnesota Timberwolves All-Star Jimmy Butler.
In his third season in South Beach, Winslow averaged 7.8 points on 42.4 percent shooting, 5.4 rebounds, 2.2 assists, and 0.8 steals while averaging 24.7 minutes per game across 68 appearances.
He played in just 18 games the year prior as a result of surgery to repair a torn labrum in his right shoulder.