The Swiss Formula One team announced their plans Thursday on the eve of opening practice for this weekend's Hungarian Grand Prix.
Team boss Monisha Kaltenborn said: "We are pleased about the extension and doing it so early shows that the drivers, and the team, are sure they are heading in the right direction.
"We have full confidence in the talents and skills of Marcus and Felipe."
Swede Ericsson, 24, joined Sauber this year following a debut season with the defunct Caterham team last year and finished eighth in the season-opening Australian Grand Prix, his best result to date.
The drivers' announcement follows Sauber's continued calls this week for an overhaul of Formula One to cut costs, level the playing field and improve the show.