Hitzlsperger extends stay with Everton
The 30-year-old midfielder, a former Germany international, signed a short-term contract with the club in October, and has played seven times this season.
"Thomas is going to stay until the end of the season. He wants to play, like everybody else," Moyes told the club website.
"We've needed him and we will continue to need him with the games we have got in the second half of the season.
"I was thinking about letting Ross [Barkley] go out on loan and Thomas's experience allowed me to do that. I just felt that keeping him was important."
Midfielder Barkley had been loaned to Championship side Leeds United for a month, Everton said on Friday.