Vahaamahinais highly-rated in France and, at just 22 years of age, has a bright future ahead of him. The former Brive forward has won six French caps since making his international debut against Australia this time last year and was a major influence in ensuring Perpignan returned to the Heineken Cup this term.
He started the convincing Round Two win over Edinburgh a fortnight ago and featured in six of Perpignan's Amlin Challenge Cup games last year, scoring a try in their quarter-final win over Toulouse.
"We are very happy to have found an agreement with Sebastien," said Clermont's sports director Jean-Marc Lhermet.
"He has exceptional potential, a great ability to move around the field, a lot of dynamism, and plenty of power with the ball in his hands.
"He is the kind of player we haven't had and we are sure that he will be a big help for us going forward in the next few years."
Bruni's arrival will soften the blow of Vahaamahina's departure for Perpignan fans, with the 24-year-old having become an important member of a star-studded Toulon squad.
The 6ft 6in back rower many have only played once in last season's Heineken Cup winning campaign but he is highly thought of at the Stade Felix Mayol and boss Bernard Laporte is desperately disappointed to be losing him next year.
"I'm extremely disappointed. He's one of the players who have played the most games for us," said a clearly frustrated Laporte.
"And he says he has the spirit of Toulon? From now on, we'll see. Until the end of the season, we'll be calling on him to play only if it's absolutely necessary."
There were contrasting emotions at Perpignan, though, with president Françis Rivière delighted to have got his man.
"Virgile has been brilliant since the beginning of the season. I am therefore very proud that he has chosen to embrace the project we have here at USAP for the next three years."