The team announced the deals Wednesday. Financial terms of the deals were not released.
Both players were set to become restricted free agents on March 13.
Jansen has had only one bad snap in three seasons with Carolina. He's handled snapping duties on more than 400 punts, field goals and extra points since being acquired in 2009 in a trade with the Packers.
Jansen's agent Paul Sheehy says, "J.J. wanted to get this done before free agency and he's certainly excited about returning to the Panthers."
Phillips played in four games last season for Carolina and notched three tackles before being placed on injured reserve with a calf injury.