WATCH Arsenal TV on beIN SPORTS | Foxtel, Kayo, Fetch & beIN SPORTS CONNECT
The Gunners agreed a reported £12million fee with the Blues for the 31 year-old midfielder and the Premier League leader got the deal over the line in time.
Arsenal, bossed by Mikel Arteta, had been pushing to sign Moises Caicedo from Brighton and Hove Albion but saw a number of bids rejected, with the Seagulls making it clear the Ecuador international would not leave this month.
The Gunners moved instead to strengthen their squad with a proven performer, swifty completing a deal for Jorginho, whose contract with Chelsea was set to expire at the end of the season.
Jorginho's arrival comes amid concern for Arsenal midfielder Thomas Partey, who was withdrawn in Friday's FA Cup defeat to Manchester City with an apparent rib injury, while Mohamed Elneny has been sidelined with what Arsenal described as a "significant" knee problem.
A Champions League winner with Chelsea in 2020-21, Jorginho was also part of the Italy squad that won the Euro 2020 title.
Arteta said of his new recruit: "Jorginho is a midfield player with intelligence, deep leadership skills and a huge amount of Premier League and international experience. Jorginho has won in his career, but he still has the hunger and huge willingness to contribute here.
"We are so pleased to sign Jorginho and welcome him and his family to the club."
Gunners sporting director Edu said on Arsenal's website: "Jorginho is an established professional with a strong mentality who brings quality and experience into our squad.
"He is a player who fits our style of play, and he joins us at a very good moment where he can contribute in a key position to help maintain our momentum. We welcome Jorginho to Arsenal."