Hoyte, whose current deal expired earlier this summer, has been training with the rest of the squad for several weeks and is expected to be in action against York City tomorrow in David McGurk's benefit game at Bootham Crescent.
"It's great to get everything signed and now I can concentrate on the new season," says the 27-year-old defender who joined Boro from Arsenal four years ago following a season-long loan with Sunderland.
"We have a lot of new faces and there is a great atmosphere in the dressing room. There is competition throughout the whole squad and that will drive everyone on to do well.
"Middlesbrough is a fantastic club and I have really enjoyed my time here. The North-East is now my second home and I feel very settled in the area.
"I really believe we can make a strong challenge this season and I'm looking forward to playing my part."
Manager Tony Mowbray says: "Justin has been training with us for a few weeks and he brings qualities to the squad, which is all about balance.
"Every player has strengths and weaknesses and I feel the balance of our squad will be enhanced by the strengths he brings. One of his qualities is his superb athleticism."
Hoyte, a former England U-21 international, has made 108 appearances since joining from Arsenal and is versatile enough to play in both full-back positions.