The vastly experienced defender has joined the Potters on a deal until the end of the season and follows Taylor Harwood-Bellis in checking in at the bet365 Stadium this month.
Jagielka's short-term contract with Derby County ended earlier this week and City moved quickly to add him to their ranks.
The 39-year-old former England international made 21 starts for the Rams this season and manager Michael O'Neill said: “Phil brings a wealth of experience to our squad and has shown with his performances for Derby that he still has a great deal to offer.
“There were no shortage of clubs who expressed an interest in signing him once his deal with Derby came to an end and we're really pleased he has chosen to join us."
Jagielka has more than 700 career appearances to his name, the majority of which came in the Premier League in a 12-year stay with Everton and two spells with Sheffield United. He's also the proud holder of 40 England caps.
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