It marks a return to single-seaters for Niederhauser, who has been racing in the Lamborghini Super Trofeo this year after a three-season stint in GP3 yielded four victories.
Berthon, who sits 14th in the GP2 standings, will miss Monza having chosen to prioritise his European Le Mans Series campaign with Murphy Prototypes this weekend at Paul Ricard instead.
Niederhauser said: "I'm extremely happy about my debut in the GP2 series.
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"I'm ready for this opportunity. It will be an enormous challenge with many new things.
"I am very grateful to those who offered me this possibility and I will give it my all to achieve as much as possible."
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