Marleau, 39, will be free to sign with any team beginning Monday. He had one year and $6.25 million left on a three-year deal he originally signed with Toronto.
The buyout was expected after Carolina had taken on Marleau's contract in a trade with the Maple Leafs last week.
Because Marleau signed as an over-35 player, the full $6.25 million hit will count against the Carolina cap.
Marleau, a three-time All-Star who ranks fifth all time in NHL games played (1,657), had 16 goals and 21 assists this past season. Among active players, he ranks second in goals (551), fifth in assists (615) and fourth in points (1,166).