Konstantinos Mavropanos trained with his new Arsenal team-mates for the first time at London Colney on Friday.
Mavropanos signed for Arsenal on a permanent deal on Thursday. The fee is understood to be around £1.8m, according to Sky sources.
The Greek defender, who had made 16 senior appearances for Greek Super League side PAS Giannina before the move, will be loaned out to gain more experience.
Arsene Wenger said on Thursday night: "He's not ready to play for us. We'll give him out on loan."
Mavropanos' arrival is Arsenal's first signing since the appointment of Sven Mislintat, formerly of Borussia Dortmund, as the club's new head of recruitment.