The Mexican international is currently Arsene Wenger's fifth-choice striker behind Robin Van Persie, Nicklas Bendtner, Theo Walcott and Marouane Chamakh and he has started only three Premier League games in three seasons at Arsenal.
Wenger has openly stated that he wants Vela to go on loan but only to a club that will play him whenever possible.
Wenger also revealed that he received numerous enquiries from Premier League clubs for the striker, but it seems La Liga club Valencia have won the race to sign him.
Vela endured loan spells in Spain earlier in his career, at Osasuna and Celta Vigo, and is set to sign a six-month loan deal at the Mestalla.
Vela has made 34 appearances for Mexico scoring nine goals and was part of the South American team's World Cup squad in South Africa last year. He started both group games before missing the final one through injury. He was an unused substitute in Mexico's defeat to Argentina at the last-16 stage.