8th January 2019, 15:58 | StHelens
The 32-year-old utility forward has made 247 appearances for Saints since joining from Harlequins ahead of the 2011 season.
“To spend 10 years at this club will be something special,” he said. “It is a privilege to have been here for so long and an honour considering I am not from the area.
“I am really looking forward to hopefully celebrating a testimonial here and, more importantly, winning silverware.”
McCarthy-Scarsbrook, who played for England before representing Ireland in the 2017 World Cup, is one of a host of St Helens players to enjoy a new lease of life under coach Justin Holbrook.
“Louie was outstanding for us in 2018,” Holbrook said. “He is a really important and versatile member of the squad who is well liked by his team-mates and the coaching staff.
“He sets a great example to the younger players in the squad with his work-rate and passion and I’m really looking forward to working with him for a further season.”