Raikkonen's future with Ferrari has been called into question this season after struggling with handling errors while Alonso too has been linked with an exit.
The Spaniard - who has two podium finishes to his name this term - has been suggested as a target for McLaren but Mattiacci says the pair will both continue next season.
Asked by Sky Sports F1 whether the line-up would remain unchanged, the Italian responded: "Yeah. We have two great drivers.
"My job is to lay down a strategy to make sure all the team share the same vision and the will to succeed in an environment that puts them in the condition to put them back at the top.
"Getting everybody motivated in a moment that definitely isn't the easiest one for Ferrari."
Ahead of the Belgian Grand Prix, Ferrari are yet to pick up a win this season though Alonso's strong showings in a struggling car have helped them to third in the constructors' standings.