The starlet will spend the duration of the 2012-13 campaign in Cataluyna, following in the footsteps of Philippe Coutinho, who recently returned from a similar arrangement
The 20-year-old passed a medical on Tuesday and will be handed the No.12. jersey, having been given permission to gain first-team experience in La Liga.
Ater making his move, Longo revealed that Philippe Coutinho played a major role in his switch, as the Brazilian talked highly of Mauricio Pochettino's side following a successful loan spell at the club last term.
"I am very happy and cannot wait to start my new adventure with Espanyol," enthused Longo.
"Coutinho told me so many positive things about the club and I'm happy to be here."