Cheddira moves to the LaLiga club on a season-long loan.
Cheddira, after coming off the bench in Napoli's 3-0 win against Bologna on the weekend, landed in Barcelona yesterday to undergo a medical with Espanyol.
The two clubs have agreed a deal over a straight loan.
Cheddira leaves Napoli to make room for the imminent arrival of Romelu Lukaku from Chelsea.