Wenger will throw midfielder Bischoff straight into Arsenal's first-team.
Bischoff, 21, turned down an increased wage offer from Bundesliga club Werder Bremen and insisted on joining Wenger.
He will arrive at the Emirates on a free but the Gunners will have to pay compensation that is yet to be decided by UEFA.
Bischoff admitted: "Bremen was superb but Arsenal is a huge opportunity for me. Wenger trusts me to be in the first-team and he has not put me under any pressure for the move. He told me to take all the time I needed."