Boro have beaten off stiff competition to capture highly-rated midfielder Adam Forshaw from Wigan Athletic.
The 23-year-old has signed a three-and-a-half-year contract and the fee is undisclosed.
Forshaw learned his trade with Everton's Academy and made two appearances with the first team, but it was a move to Brentford that saw his career take off.
Named Brentford's Player of the Season in the 2013/14 campaign, he joined the Bees in February 2012, but a loan period turned in to a full-time deal that summer and he went on to make 100 appearances for the club.
Forshaw made the move to Wigan in September and has made 17 appearances for the Latics this season, including one against Boro in November.