The 28-year-old is set to join Boro on a permanent transfer worth a reported £2.8million, with half of the fee going to his former club Reggina
A statement from Espanyol read: "The Uruguay striker will join Middlesbrough once he passes a medical and signs his contract with the English club.
"In the next few days, Stuani will no longer be an Espanyol player as a preliminary agreement exists for the player to leave our club.
"The intention of the forward is to join Middlesbrough, coached by Spanish manager Aitor Karanka.
"The Uruguay international was expected to join our team in training this week but the player has been given permission not to do so in order to aid his transfer to his new team.
"The player's wish is to say goodbye to his team-mates next week in Barcelona before joining his new club."
Stuani was part of his national team's squad at the recent Copa America in Chile
The forward scored 16 goals in 48 appearances in all competitions for Espanyol in the 2014-15 campaign to help the Barcelona-based outfit finish 10th in La Liga.
Boro finished fourth in the Sky Bet Championship last season.
Source : PA
Source: PA