Neymar broke the news of his desire to leave Barcelona at Lionel Messi's wedding in June, according to former team-mate Xavi.
The Brazil international joined Paris Saint-Germain in August for a world-record fee of €222 million after many weeks of speculation over his future.
The forward insisted at his unveiling he only made the decision to accept PSG's proposal two days before the deal was completed, but Xavi says he made it clear he wanted out at Camp Nou while at the lavish wedding of Messi and Antonella Roccuzzo in Rosario.
"He said to us at Messi's wedding that he wanted to change," the former Barca star told the BBC World Service.
"I said to him: 'But, why?' [He said] 'I'm not happy in Barcelona, I prefer [to] go out, to have a new experience at Paris Saint-Germain. Finally, it was his decision. We must respect it."
Neymar has enjoyed a spectacular start to his career in France, scoring nine goals in all competitions for Unai Emery's side.
His latest strike came in the 4-0 win away to Anderlecht in the Champions League on Tuesday that moved PSG to nine points from nine at the top of Group B.
Kylian Mbappe was also on target in that victory and Xavi believes the rising France star and Neymar make PSG clear candidates to win Europe's top trophy for the first time in 2017-18.
"I think, with Neymar, with Mbappe, Paris Saint-Germain have a great chance to win the Champions League this season," he added.