The 25-year-old had earlier paid his a 222 million-euro ($264 million, £201 million) buyout clause.
Neymar signed a contract that will see him stay at the French club till 2022.
The club tweeted;
“Paris Saint-Germain are absolutely thrilled to announce the arrival of @neymarjr !!! ”
— PSG English (@PSG_English) August 3, 2017