Boyle, 31, roughly doubles his current salary after stating that he wanted to remain in Tampa long-term.
In 17 games with the Bolts this season, Boyle has notched three goals and eight assists for 11 points.
Boyle has played in 503 career NHL games and has registered 75 goals and 203 assists for 278 points.
Meanwhile, the Lightning acquire a young defenseman for Prospal, who is set to become an unrestricted free agent this summer.
"Alexander Picard is a young prospect with good size and excellent hockey sense who has played in the NHL," said Tampa GM Jay Feaster. "We believe he has a significant amount of upside in his future. In moving Vaclav Prospal we wanted to add to our organizational depth, and by acquiring both a young defenseman and a future draft pick we were able to achieve that goal."
In 62 games with the Lightning this season, Prospal registered 29 goals and 28 assists for 57 points.
Picard, 22, has played in 53 games with the Philadelphia Phantoms of the American Hockey League this season and ranks second on the team, first among defensemen, in points with 38.
