The Italian midfielder entered into the final six months of his Chelsea contract.
He made more than 200 appearances in his five-year spell for the Blues.
The 31-year-old signed a deal until the summer of 2024 and made his debut against Everton last week replacing Thomas Partey in the 59th minute.
The Euro 2020 winner is expected to play a key role for Mikel Arteta as Arsenal challenges for the Premier League title.
Premier League legend Alan Shearer lauds Arsenal’s decision to sign the experience midfielder this January.
‘Arsenal are a very, very good team with a really bright and intelligent manager in Mikel Arteta,’ Shearer said on BBC Radio 5 Live.
‘I really do like the Jorginho signing. He will bring a wealth of experience and that know-how to win and to get over the line.
‘They are still going to be big questions and big times to navigate over the coming months.
‘So who better to get in January than a guy like Jorginho who has been there and done it at every level.’
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