The big money move dwarves the previous record fee paid by an Italian club - the 55 million euros Lazio paid Parma for another Argentina frontman, Hernan Crespo, in 2000.
Higuain's move was confirmed on the 'transfers' section of the official Serie A website on Tuesday. It has been reported that, after a season in which he scored 36 league goals, Napoli slapped a buyout clause on the 28-year-old’s contract.
If 90 million euros is the fee paid, Higuain will become the world’s third most expensive player, behind Real Madrid pair Cristiano Ronaldo (94 million euros) and Gareth Bale (101 million euros) on the all time list.
Reports on Tuesday said Juve CEO Beppe Marotta had negotiated with Napoli president Aurelio De Laurentiis to pay the transfer fee over two instalments.
After leaving the offices of Serie A, Marotta gave no details when asked by waiting media but confirmed the move when he said: "We've deposited Higuain's contract (with league officials). We've concluded everything."
After Alvaro Morata returned to Real Madrid earlier in the summer, Higuain is expected to partner fellow Argentina striker Paulo Dybala, who in his maiden season with Juventus was their top scorer with 19 league goals, when the club return from their pre-season tour of Australia.
Higuain joined Napoli from European champions Real Madrid in a 40 million euro deal in 2013 and the size of the fee agreed on Tuesday may suggest Juventus are expecting to see the departure of French midfielder Paul Pogba, who appears set to join former club Manchester United.
Pogba’s fee is expected to break the world record, with some Italian media reporting that the asking price is now 125 million euros.