Harper has joined the Black Cats on a deal until the end of the season.
Sunderland boss Sam Allardcye has brought in Harper to compete with Jordan Pickford and Vito Mannone.
Allardyce said: “Steve will be a positive addition to our goalkeeping stable.
“He has vast experience at the top level and that can only be beneficial to Vito and Jordan as they continue to develop.
“He knows the club well and, as an Easington lad born and bred, he needs no introduction to Sunderland.”
