Boyle played in 25 games for the Panthers this season and had three goals and three assists and a minus-1 rating.
"Dan is a gifted offensive defenseman," Lightning General Manager Rick Dudley said. "We've been looking to generate more offense from the blue line and work on our passing out of our zone, and those are his fortes. Dan makes a good first pass up the ice, is strong on the power play and is capable of playing both defense and forward."
Signed as a free agent by Florida in March 1998, the 25-year-old Boyle has recorded 10 goals and 29 assists in 129 games over the past four seasons with the Panthers.
The Lightning on Monday also assigned defenseman Kristian Kudroc to Springfield of the American Hockey League.