Seth Costello is a fictional character from the British television soap opera Hollyoaks, played by Miles Higson. He made his first appearance during the episode broadcast on 20 July 2010. His first major storyline was in 2011 when he was the centre of a steroids storyline. He also became involved in the storyline where his father Carl Costello (Paul Opacic) began an affair with Mercedes McQueen (Jennifer Metcalfe). 2020 saw the return of Seth, when he blackmailed the McQueen family with grandfather Silas Blissett (Jeff Rawle). He departed again on 2 February 2021.