Winston Reid scored a late winner for West Ham at the London Stadium as Sunderland's winless start extended to nine games.
The hosts may well have had a penalty when Reid was wrestled to the ground by Javier Manquillo early on.
Dimitri Payet then drew a smart save from Sunderland keeper Jordan Pickford before firing a low strike against the post after some clever footwork on the edge of the box.
Wahbi Khazri had the visitors' best chance after Steven Pienaar's deflected pass put him through on goal, but his tame shot was easily saved by Adrian.