Winston Reid scored a stoppage-time winner for West Ham United at the London Stadium as Sunderland's winless start went on.
Sunderland looked on course for a point but Reid struck an effort from outside the area in the 94th minute.
West Ham had twice gone close to scoring through Dimitri Payet who, after a superb run, saw a shot saved by Jordan Pickford and hit an upright.
Patrick van Aanholt fired wide for Sunderland after a one-two with Jermain Defoe, whose 20-yard effort was saved by Adrian while Jack Rodwell headed a corner over.
Simone Zaza had an overhead kick narrowly miss, having seen an earlier strike deflect wide.
Sunderland almost made a flying start to the second half when Wahbi Khazri went through, only to shoot straight at Adrian and Reid punished the Tunisian's miss at the death.
WHO'S GOING TO BE YOUR
MAN OF THE MATCH?
Vote at Full-time