Neymar is ready to officially sign the deal which was originally agreed in June, the club have announced.
Neymar joined Barca in 2013 and his terms at Camp Nou were due to expire in 2018, but the fresh agreement will see him tied to the Spanish champions for the next five seasons.
The 24-year-old has won two LaLiga titles, two Copas del Rey, the Champions League, Club World Cup and Supercopa de Espana in his first three campaigns.
He was heavily linked with Paris Saint-Germain prior to agreeing the new contract ahead of a 2016-17 season that has seen him score five goals in eight appearances.
"Neymar will make his contract extension official on Friday 21 October at 3.00pm CET at the club offices," read Barca's statement on Monday.
"As the club has already announced, the striker's contract extension with FC Barcelona will tie him to the blaugranes until 30 June 2021."
Prior to the contract becoming official, Neymar is expected to be involved as Barca host former head coach Pep Guardiola and his Manchester City side in the Champions League on Wednesday.