Last season's double Player of the Year ended months of uncertainty about his future by signing the contract this morning and goes straight into the squad for tomorrow's Championship trip to Leeds.
"It's fantastic news," said Tony Mowbray. "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."
Arca, 30, won the Middlesbrough Official Supporters' Club Player of the Year poll last season and was also Players' Player of the Year.
The Argentine midfielder joined Boro from Sunderland in 2006 and has made 129 league appearances for the club, scoring seven goals.
Source: Northern Echo
Source: Northern Echo