Adam Forshaw says it was an easy decision to sign an extended contract at Boro.
The midfielder, 24, has made more than 50 Boro appearances since arriving from Wigan Athletic in January 2015.
Now, the former Everton youngster has penned a deal which extends his stay at the Riverside until 2020.
"I'm delighted. I've enjoyed my time at the club since I've been here," Forshaw said.
"My teammates, the staff, the fans, everyone around the area has been really supportive.
"It was a bit of a no-brainer when the contract came up."
Forshaw says that a new deal has been in the works since before Boro earned promotion to the Premier League in May.
"The club spoke about it to me and my agent at the back end of last season," he said.
"It was nice to go into the summer break knowing that if I came back and worked hard, hopefully that would be on the table.
"Fortunately, we've got it done early in the season, so I can put it to one side and concentrate on the games."
The midfielder has featured in all three of Boro's games so far this season, replacing the injured Marten de Roon in the Premier League opener against Stoke City, and playing the full 90 minutes the following weekend at the Stadium of Light.
"It's been good, the results have gone well so far," he said.
"It was unfortunate that Marten got the injury, but I've had my chance now and I'm enjoying it.
"There is a lot more quality in the league and you have to be a lot better on the ball because you get punished if you lose it.
"I think we're all learning, especially the lads in our first year in the Premier League. It's been a positive start.
"We're just taking it one game at a time. We want to keep improving, and show what we can do."