The former Aston Villa and West Ham man has signed a deal to keep him at Goodison Park until January and is available to face QPR on Sunday.
The 30-year-old, who has had previous playing spells in the Premier League with Aston Villa and West Ham, had been without a club since his contract with Wolfsburg expired at the end of last season and was thus permitted to sign outside of the transfer window.
The former Germany international has signed in time to gain international clearance and is available to be a part of the matchday squad to face Queens Park Rangers on Sunday.
Hitzlsperger had been training with Everton since the start of the season and featured recently in an Under-21 league game as an allocated over-aged player. The German's last stint in England came in 2010, when he signed for West Ham on a free transfer, but he was unable to make his debut until February, 2011, because of injury.