The 25-year-old becomes the second striker in the past few hours to join the club after Sevilla confirmed the signing of Luciano Vietto from Atletico Madrid.
Ben Yedder played 174 times for Toulouse, scoring 71 goals. He also scored 17 goals in 35 games in Ligue 1 last season.
Sevilla boss Jorge Sampaoli clearly saw the need to bring in reinforcements to his attack with the departure of Kevin Gameiro to Atletico Madrid.