Jones-Buchanan is 37 and marks his 20th year next year since debuting for his hometown club while fellow back-row Ablett turns 33 next month.
But the one-club duo – who have won countless trophies with Rhinos – will play on for Rhinos in 2019 and winger Luke Briscoe, 24, has also signed a three-year deal after re-joining from Featherstone Rovers earlier this season.
“We are pleased to be able to offer all three players new contracts,” said Sinfield.
“Jamie and Carl are outstanding clubmen who epitomise the culture and ethos we cherish here at Leeds. However, more importantly both players are still able to do a valuable job for the team on the field as well and have earned their new deals.”
He added: “There has never been any question over Luke’s ability. However his early career was frustrated by injuries. He is a great example to any young player who suffers a setback.
“He has continued to work hard, listen to his coaches and give his very best and deserves this contract with the Rhinos.”