Sources close to the Catalan club have confirmed to Goal that Cucurella will seal a permanent move to their Liga rivals in a deal worth up to €10 million (£9m/$11m).
That will see Ernesto Valverde's side make a profit on a player they confirmed they had re-signed from Eibar on Tuesday for €4m.
That played a big part in Cucurella deciding to join the Madrid-based club, where he is likely to be given more exposure to the first team than he would have had at Barca, who already possess Jordi Alba in that position.
The decision to sell the former Spain youth international does mean that Barca will look to recruit an alternative back-up option for the left side of defence, with Real Betis defender Junior Firpo on their radar.
The 22-year-old made 24 appearances in Spain's top flight for Betis last season and any deal for the defender is likely to include Juan Miranda heading in the opposite direction.
It remains to be seen if Barca will make any further additions in the summer transfer window having already splashed out on Antoine Griezmann in a deal worth €120m (£107m/$134m) from Atletico Madrid.
Frenkie de Jong has also arrived from Ajax and, while Neymar remains a target, Paris Saint-Germain are refusing to sell the Brazilian for anything less than the €222m (£200m/$249m) they paid to sign him from the Catalans.
AS reported on Tuesday that Barca had indeed made a bid worth €40m (£36m/$45m) plus Philippe Coutinho and Ousmane Dembele for the forward that had been rejected by the Parisians.
Sources close to the Liga champions have told Goal that, despite Barca's interest and the 27-year-old's desire to re-join them, he is yet to meet the stipulations set when their interest was first established in November 2018.
That includes the acceptance that he made a mistake in leaving Catalunya for Paris in the first place, that he agrees to a wage cut when the time comes to negotiate a contract and that he drops various legal proceedings against the club.
Their 2019-20 La Liga campaign kicks off on August 16 with an away fixture against Athletic Club.