The Gunners completed a deal to sign the Greece international from Bundesliga giants Borussia Dortmund on Monday evening.
Sokratis will be hoping to improve the Arsenal defence following their disastrous performances throughout the 2017-18 season.
Arsenal signed former Borussia Dortmund duo Aubameyang and Mkhitaryan in the January transfer window to improve the Gunners’ attack.
Sokratis played with the attacking duo during their spell together under current Liverpool FC manager Jurgen Klopp at the Bundesliga.
Speaking to the club’s website about linking up with his former Dortmund team-mates at the north London side, Sokratis said:
“Yes it’s a little bit [strange] but it’s also very beautiful that I’ve come to one team but I also have two players who I was together with for a lot of years.
“I know them both very well and I’m very happy.”
Arsenal finished in sixth spot in the Premier League table last term after the Gunners missed out on a Champions League spot for the second successive season.
The north London side lost 3-0 to Premier League champions Manchester City in the League Cup final at Wembley.
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