Scott McDonald netted the winner for the Championship side in the 39th minute when he turned in Ishmael Miller's drilled centre at the near post.
Sunderland started brightly with Adam Johnson almost catching out Boro keeper Jason Steele direct from a corner before Louis Saha blazed over.
The visitors then made their mark as Faris Haroun's shot from a tight angle was saved by Keiren Westwood and McDonald fired just over from 25 yards.
Miller also fluffed a good chance and McDonald clipped the top of the crossbar with a dipping strike before the pair combined to put Middlesbrough ahead.
Steven Fletcher had been kept in check by the Boro defence and he could only head tamely into Steele's arms when he was finally presented with a chance from Johnson's cross shortly before the interval.
Sunderland were fired up after the restart and Fletcher forced a low save from Steele with a shot from the edge of the area.
Stephane Sessegnon then saw a header well-taken by Steele before shooting just wide from 20 yards.
But the Boro defence held firm and the visitors almost nicked a second goal on the break with Haroun and McDonald both denied by good saves from Westwood.
The hosts pushed hard for a late equaliser but Sessegnon could only head weakly into the side-netting and Fletcher just failed to latch on to Fraizer Campbell's flick-on.