That’s according to Spanish news outlet Super Deporte who say Mourinho has agreed to let him leave following talks with Valencia supremo Peter Lim.
The Belgian-born 21-year-old – who has represented Brazil at youth level – has only made a handful of appearances for United since progressing from the academy.
He had a loan at La Liga side Granada last term and played an important role in their season having racked up 35 appearances.
And it now looks like another temporary move is on the cards.
Reports earlier this week suggested Mourinho was reluctant to sanctions Pereira’s exit.
But Lim, who has close links to the club through the Class of ’92 legends, appears to have twisted the Portuguese’s arm.
Speaking during pre-season, Pereira suggested he was vying for starting spot with the Red Devils.
“Man Utd star Andreas Pereira looks set to join Valencia ”
“It was a good experience [at Granada],” he said.
“I learned a lot of things and hopefully I can use them now here back at United.
“It boosts me that the people here trust the young players.
“I am very happy for the young players and I want to be a part of this team as well.”
Perez was snapped up form Deportivo de La Coruna last summer but has struggled to settle in north London.
A return to La Liga now looks on the cards following Alexandre Lacazette’s arrival at the Emirates.