The deal, which the Predators announced via their official team Twitter account, includes veteran forward Olli Jokinen, prospect Brendan Leipsic and a first-round pick in 2015 going to Toronto in exchange for Franson and Santorelli.
Franson and Santorelli are both pending unrestricted free agents and were rumored to be among the top targets on the market with the NHL's trade deadline of March 2 approaching. Both players began their NHL careers with the Predators.
"In preparation for the 2015 playoff run, our goal was to add a veteran defenseman who could play in all situations and a proven forward who could move up and down lineup based on the situation," Predators general manager David Poile said in a statement. "We were fortunate to do this in the same transaction with players who are in the prime of their careers more than two weeks before the trade deadline in order to give them more time to contribute and gel with their teammates.
"Both Cody and Mike were drafted, developed and began their NHL careers here. They know our organization and still have former teammates and friends on the roster. We are fully confident that they will seamlessly fit into our team."
Nashville is currently leading the NHL with 82 points. Prior to the trade, many speculated that Poile would be among the most aggressive in advance of the deadline.
Santorelli, 29, has 11 goals and 18 assists this season.