The 25-year-old striker - who has earned 31 caps for Albania - was on Inter Milan's books as a teenager and joined the Catalan club from Albacete in January 2020.
He appeared on the Barca bench once, but played the majority of his football for Barcelona B and spent last season on loan at Spezia in Serie A.
The length of his contract at Vicarage Road has not been revealed.
