"Las Palmas and Hamburg have today agreed a loan deal for Croatia international Alen Halilovic until the end of the 2017-18 season," the club, who are 11th in La Liga, said in a statement on Thursday.
"In the loan contract the club reserves an option to buy the 20-year-old."
The playmaker made his Croatia debut aged 16 in 2013 and then signed for Barcelona from Dinamo Zagreb on a four-year deal.
He spent a single season at the Nou Camp, predominantly playing for the club's reserve team in Spain's second tier.
Halilovic spent the 2015-16 campaign on loan at Sporting Gijon, where he played regularly and helped them avoid relegation.
Barcelona sold him to Hamburg last year for a fee reported to be 5 million euros (4 million pounds), although the Catalans retained a 10-million-euro buy-back clause.
He only made one Bundesliga start for the German club, who have spent most of the campaign fighting a relegation battle.
(Reporting by Richard Martin; Editing by Toby Davis)
