The 150th meeting between the two rivals - and the first in four years - was settled by Riley McGree's goal midway through the first half as Chris Wilder's side picked up only their second win of the season.
Sunderland, meanwhile, missed the chance to move as high as fourth place as they fell to their first defeat under new boss Tony Mowbray - a former Boro player and manager himself.
It may have been different had the Black Cats capitalised on an early chance when Ellis Simms poked the ball to Alex Pritchard, who scooped his hurried effort well off target when he had more time than he realised and only the keeper to beat.
McGree could have had a hat-trick in the first half alone, missing presentable opportunities either side of his goal, including a tame side-footed effort straight at the keeper shortly before half time.
It was the midfielder who had the decisive say in the match, though, expertly taking Ryan Giles's cross from the left in his stride before toe-poking his finish past Anthony Patterson, despite Luke O'Nien getting a foot to the ball with an attempted last-ditch challenge.
Rodrigo Muniz and Duncan Watmore both tested Patterson in a second half short of clear-cut chances, with Sunderland struggling to pose any real threat to the Middlesbrough goal in the absence of top-scorer Ross Stewart, who was forced to watch from the stands after picking up an injury in the warm-up.
The result means that Boro remain unbeaten at home in the league this season, although this is their first clean sheet in front of their own fans since April and only their second in their last 12 home outings.
Sunderland, meanwhile, remain eighth having now won only two of their last 26 visits to Middlesbrough, including 1-0 defeats in each of their last three such matches.