Kehrer has made 128 appearances for PSG in four years since arriving for £33 million from Schalke.
He has started for Germany regularly for the last year and has 22 international caps.
Kehrer, who signed for an alleged £10.1 million, stated, “This is the finest league in the world, and I’m delighted about going to play in the Premier League.”
“I spoke with the manager, and he explained how he saw me integrating into the team. My main objective right now is to fit in, become a part of the club, and enjoy playing for West Ham.”
Kehrer played 34 times for the French champions last season and has the option of another two years on his contract.
He started their Champions League final loss to Bayern Munich in 2020 and won three Ligue 1 championships in addition to two French Cups.
David Moyes, the manager of the Hammers, described the player as “a skilled player who can play in a variety of defensive positions, adding strength and depth to our present options.”
Chelsea and West Ham are negotiating over Emerson Palmieri, a full-back from Italy.
Injuries to the new hire This season, Moyes has been obliged to use Ben Johnson in center defense in addition to Kurt Zouma due to Nayef Aguero, Craig Dawson, and Angelo Ogbonna, a veteran partnership.
After winger Maxwell Cornet, attacker Gianluca Scamacca, defender Nayef Aguerd, midfielder Flynn Downes, and goalkeeper Alphonse Areola, Kehrer is West Ham’s sixth summer acquisition.