The 20-year-old had been expected to form part of Barcelona's first-team squad this season following a successful loan spell with Everton last term.
However, Barca boss Luis Enrique took the decision to send the youngster on loan to Sevilla.
"I'm very happy to be here. My departure from Barcelona was a little surprising, as was the decision of Luis Enrique, but I want to enjoy this season," Inside Spanish Football quotes Deulofeu as saying at an official press conference.
"One of my aims is to prove to Luis Enrique that he's made a mistake and now I want to focus my efforts here at Sevilla.
"I think this is an important season for Sevilla and I'm not thinking about anything beyond this campaign. All I'm thinking about is making the most of my time here, learning at this great club and helping achieve our objectives."
Denis Suarez also moved on loan from Barca to Sevilla this summer.