Elliot Embleton scored the only goal of the game five minutes before half-time when he was set up by Ross Stewart.
After a shaky start, the Black Cats were more assured after the break to claim a much-needed three points.
New signing Danny Batth also made his debut in the heart of the Black Cats’ defence.
Our chief SAFC writer Phil Smith has delivered his verdict on how each Sunderland player fared:
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1. Thorben Hoffmann - 6
This is how it played out as Sunderland seal a crucial and hard-fought win over Portsmouth Photo: JPI Media
2. Tom Flanagan - 6
Got away with one or two sloppy clearances but also made some strong interventions late on. 6 Photo: JPI Media
3. Danny Batth - 8
A superb display on debut. Kept it simple on the ball, made some good challenges and barely lost a header over 95 minutes. Some impact. 8 Photo: SAFC
4. Callum Doyle - 7
A strong and mature performance. Brought the ball out when he could and defensively got through his work well. Strong in the air, an improving part of his game. 7 Photo: Frank Reid