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.
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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 QPR 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 was unable to make his debut until February 2011 because of injury.