The Algerian international, 35, has been training with the Blades for a number of weeks and has now penned a deal. He will be added to the squad for the club's home game with Preston on Tuesday.
Guedioura has previously worked with Blades chief Slaviša Jokanović at Watford and Qatari outfit Al-Gharafa and also spent time in the Championship with Wolves, Nottingham Forest, Crystal Palace, Watford and Middlesbrough.
He said: "I'm very pleased to have signed and I can't wait to play for the team. It's something special for me to come back to the UK, so I am really happy.
"I'd like to thank the manager and the club for allowing me to come to train and have the opportunity to show what I can do. I am really happy to end up with a contract now until the end of the season, so I am up for the challenge and ready to start."
Jokanović added: "Adlène is someone I know really well. He has completed three weeks training with us and I believe he can bring something positive to the team.
"I have worked with him before; he knows many players here, playing against them and he knows the competition. He will be an important man in the dressing room."
Guedioura joins Robin Olsen, Morgan Gibbs-White, Conor Hourihane and Ben Davies as new faces at the club this summer.