The 28-year-old joined the Red Devils from Hull KR ahead of the 2020 season and has played in 10 of their 13 league and cup games so far this year.
Salford coach Richard Marshall said: “I’m really pleased to see Chris pen a new deal with us. He’s a quality player and a brilliant individual off the field.
“He’s been one of our most improved players this year and has really bought into our plans and the direction that our club is heading.”
Atkin said: “It was an easy decision to make when I sat down with the club.
“Salford has quickly become my home since I arrived here last year and everyone at Salford has always made me feel welcome and valued, our loyal fans included.
“I’ve enjoyed my time here so far. We’ve got a brilliant set-up at Salford and I’m really looking forward to the future.”
Salford director of rugby and operations Ian Blease added: “To have Chris with us for the next two years, possibly three, is fantastic news for all involved at Salford.
“Chris is a key member of the squad and it’s great to know that he will continue to be!
“We are continuing our search for more additions for 2022 as we aim to push on from our success in recent years.”
Atkin has made almost 200 career appearances for Swinton, Hull KR and Salford. He won two caps for England Knights in 2018.