The 20-year-old spent last season with Everton but will be remaining in La Liga this year after joining Unai Emery's side.
Deulofeu spent last season at Everton, scoring three goals in 25 appearances in the Premier League, and returned to Barcelona this summer looking for first-team opportunities.
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But after coach Luis Enrique decided another campaign on loan would be beneficial, a deal was reached with the Europa League winner. Sevilla confirmed Thursday that the loan was finalized.
Deulofeu has played six times for Barcelona, with two of those appearances coming in La Liga.