The 25-year-old Wales star has been with the Ospreys for seven seasons and has played a major role in two Magners League triumphs in that time, as well as winning an Anglo-Welsh Cup back in 2008.
Hook was one of the key performers during the Ospreys' Grand Final win over Leinster last May and the Liberty Stadium outfit had understandably hoped he would remain in Swansea after his current deal expired in the summer.
And while Hook has decided to move on, his agent Derywn Jones has made it clear that the Ospreys did all they could to hang on to the versatile back.
"James has been considering his options for the last 12 months," said Jones.
"Perpignan approached the Ospreys last season and offered to buy him out of his contract. The Ospreys quite sensibly said they wanted to keep it.
"From an agent's perspective there is nothing the Ospreys or any other club in the UK could have done to keep him. It is not a negative on their part.
"I would like to thank the Ospreys because they were thoroughly professional in how they dealt with this.
"We have spent time going to France to see clubs and Perpignan is a wonderful location. The weather is great, the rugby is fantastic, they have great support and you look at the track record of players like Stephen Jones and Gareth Thomas who have gone to France and done exceptionally well and possibly come back better players.
"I am not saying there is going to be a mass exodus of players to France. But certainly now and again it can benefit a players career and hopefully it will be a great experience for James. He is young, he has a young family and if there is a time to do it, it is probably now."
Hook will hope to bow out on a high by guiding the Ospreys to back-to-back Magners League crowns before embarking on a new challenge which he says he thought long and hard about.
"It has been a tough decision but I'm really excited about the move," said Magners League Ambassador Hook at the announcement in Portmeirion today.
"I've thought about it a lot over the last year and I feel the hard grounds and surroundings will suit me.
"I met the president and the club really appealed to me. I went out there last summer, played there with the Ospreys and it is a great place to play.
"I spoke to Stephen Jones and also Nathan Hines who was out with the Lions and he played for Perpignan. They could not speak highly enough about playing out there. I took all that on board - I respect Stephen as a player and a bloke.
"Everything really appealed to me. There are plenty of reasons and I am looking forward to it.
"The last few months I have known in my head I am going, the last year has been tough. It is a huge decision, it is not just me involved, it is my fiancé Kim and my little boy Harrison as well. Obviously, it is a rugby decision as well. But the positives far outweigh the negatives."
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