He suffered the injury Monday night in the Dolphins' 41-14 loss to the New York Jets.
Seau, 35, a 12-year veteran and former all-pro, finishes the season with 57 tackles and one sack in eight games.
He is scheduled for surgery Thursday, and has been placed on injured reserve.
"I am going to head back home to San Diego and have my local doctors there, who have been treating me for 12 years, work on it," Seau said Wednesday. "The rehab should take about four months, so that will be the end of my season."