Dortmund says the transfer is agreed "in principle" and the 25-year-old will join Sevilla upon completion of a medical "initially on loan" through June 2016.
Immobile joined Dortmund from Torino for 18.5 million euros (then $25 million) in June 2014 but struggled to compensate for Robert Lewandowski's departure to Bayern Munich. He managed just three goals in 24 Bundesliga games, having finished the season before as Serie A's top-scorer with 22 goals.
Kicker reports Sevilla is paying 3 million euros ($3.3 million) for the one-year loan and that Immobile is unlikely to return to Dortmund once it's over.
The Spanish side was reportedly unwilling to meet Dortmund's 15 million euro (‚¬16.7 million) asking price for a full transfer.