Fiji backrower
The 23-year-old, who has five caps, is still in his first season with Clermont but his new contract will bind him at the European Champions Cup quarter-finalists until 2020.
"Peceli has exceptional physical qualities even if he is still young. He is capable of having the 'X Factor' that we are looking for," said coach Franck Azema.
"He will become increasingly important in the years to come."
Yato played at centre when he first joined the Clermont academy in 2013. So far, he has played 36 matches for the senior team, scoring 12 tries.
Meanwhile, fellow Fiji international forward Jone Qovu extended his contract with title-chasing La Rochelle by two more years on Friday.
The 31-year-old, who had 13 caps, will stay at the club until June 2019.