New Middlesbrough boss Gordon Strachan is struggling with injuries to strikers Jeremie Aliadiere and Caleb Folan and has been looking to bring in a new striker.
“We have a young squad so his experience will be important and he has already made a good impression in training this morning,” Strachan told the club’s official website.
While Bent added: “This is a good step for me. Middlesbrough are a big, established club and everything about the club is geared to going back up.
“The gaffer was a big influence on my decision too. He is very experienced and motivated, so I’m looking forward to playing for him.”
