The 30-year-old’s previous deal expired at the end of last season, but the Argentine star wanted to remain at the Championship side.
Boro manager Tony Mowbray told the club’s official website: “It’s fantastic news. Julio was outstanding last season and I’m delighted he has decided to extend his career at Boro.
“He is popular with the fans and in the dressing room and he is a player I value for the skill and experience he can bring to our team.”
