Steve Cotterill enjoyed a dream start to life as Nottingham Forest manager as Middlesbrough lost in the Championship for the first time this season.
Marcus Tudgay put the home side in front after 35 minutes when he fired home Chris Gunter's right-wing cross.
Midfielder Lewis McGugan doubled the lead after a scramble which saw Ishmael Miller, twice, and Radoslaw Majewski have shots blocked.
It was Forest's first home win in the league this season.
Boro offered little - especially in a lacklustre first half - and Forest could have extended their lead when Wes Morgan flashed a header wide of the goal.
The visitors' best chance was a header from Nicky Bailey which went wide, while Forest keeper Lee Camp saved from Justin Hoyte late on.
Forest though, showing two changes from the side beaten at Coventry, could have had more than just two goals, most notably when Miller diverted a Luke Chambers effort over the crossbar.
The home side climbed out of the relegation zone with the win, while Boro lost ground on leaders Southampton.
They also had midfielder Barry Robson booked for the fifth time this season, incurring a one-match ban for Saturday's top-of-the-table clash with Derby.
Forest manager Steve Cotterill: "It's a good start for us. I'm really pleased for the old chairman, I'm pleased for the new chairman, I'm pleased for our players and I'm pleased for our supporters because it hasn't been too fruitful a start to the season.
"But to get a victory against a very, very good Middlesbrough team is a great start because they are a good team and we're still a bit behind them.
"While we've won tonight, we're still a bit behind them and there's lots to do. But in the meantime we can certainly enjoy the next 24 hours before we get back to work."
Middlesbrough boss Tony Mowbray told BBC Tees: "There were not many positives of course, a disappointing performance and result.
"No excuses, we didn't perform in the first half. I don't remember us having a shot on goal, and the second half wasn't much better.
"Give them credit, they scored a great first goal, great bit of movement, but we will put it behind us quickly and move on to Saturday."