Junior Firpo played 29 matches for Real Betis last season, scoring three goals
Barcelona have completed the signing of Spain Under-21 left-back Junior Firpo on a five-year contract from Real Betis for a fee which could rise to £27.5m.
The Spanish champions have included a £183m buy-out clause in the Dominican-born 22-year-old's contract.
Firpo featured in 29 games last season and was part of Spain's U21 European Championship-winning side in June.
Barcelona previously signed France forward Antoine Griezmann from rivals Atletico Madrid for £107m in July.
Ernesto Valverde's side have also been bolstered by the additions of Frenkie de Jong from Ajax for £65m, goalkeeper Neto from Valencia and defender Emerson from Brazilian side Atletico-MG.
On Tuesday, the club sold Brazilian winger Malcom to Zenit St Petersburg for £36.5m after one season at the club.
Find all the latest football transfers on our dedicated page.