The 41-year-old spent five seasons on Wearside, where he made 70 appearances and scored 12 goals before his move to Oxford United.
A statement on the club's official website read: "Gateshead have today announced that former Sunderland and Oxford United striker David Rush has joined the club as assistant manager.
"The 41-year-old former team-mate of new Gateshead boss Anth Smith played in the 1992 FA Cup final against Liverpool for hometown club Sunderland.
"Former reserve team manager Paul Bryson meanwhile has returned to the club as Head Coach.
"Bryson rejoins his hometown club after leaving in the summer and has a wealth of experience in the North East non-league and junior scene."