The Championship club have announced the 29-year-old has signed a deal at the Vitality Stadium until the end of the season.
Wilshere, who spent a season on loan with the Cherries in 2016-17, has been without a club since leaving West Ham last October.
Wilshere is hoping to reignite his career after a number of frustrating, injury-hit years.
He had been training with Bournemouth in recent weeks ahead of his signing as a free agent.
Wilshere told afcbTV: “It feels great to be back and I can’t wait to get started.
“From the minute I walked through the door three weeks ago, it felt natural and like I had never been away.
“I’ve been impressed by the coaching staff, the way they work and the ambitions of the club to get back in the Premier League.”