Tony Mowbray’s side created the better chances in a goalless first half, despite losing captain Corry Evans to an injury.
The Black Cats then took the lead five minutes after half-time when Ross Stewart was awarded a penalty, resulting in a red card for Boro defender Dael Fry.
Stewart’s initial spot kick was saved by goalkeeper Zach Steffen, yet the striker was able to convert the rebound.
Amad then secured the win for the hosts when he beat Steffen with a low finish nine minutes from time.
Here’s how Phil Smith rated each Sunderland player at the Stadium of Light:
9. Amad - 8
Middlesbrough couldn’t contain him in the first half but he just couldn’t find the final touch and missed a glorious opportunity. Surprisingly quiet in the second, right up until the moment he scored a wonderful goal. 8 Photo: Frank Reid
10. Jack Clarke - 6
Drove into dangerous areas and caused Middlesbroiugh a lot of problems, just struggled with the end product on this occasion. Really good energy. 6 Photo: Martin Swinney
11. Ross Stewart - 7
Led the line excellently and caused Middlesbrough all sorts of problems. A touch fortunate with the penalty but deserved his goal and could have had one or two more. 7 Photo: Frank Reid
12. Edouard Michut (sub) - 7
Caught on the ball once or twice but generally very impressive in a tense and high-tempo game. Carries the ball well and generally precise in his passing. Denied a goal only by a brilliant McNair block. 7 Photo: Frank Reid