The former Estudiantes man, 28, has had a year of near misses, playing in losing World Cup and UEFA Europa League finals - although he did win the Primeira Liga title in Portugal.
The midfielder will enter 2015 in La Liga - his first stint in Spain - despite being linked with Premier League powerhouse Manchester United, and his move to the Mestalla will be confirmed on Friday pending a medical.
"Valencia Club de Futbol and SL Benfica have reached an agreement for the transfer of Enzo Nicolas Perez, on a permanent deal that will be made official on January 2nd, 2015," a club statement read.
"The move is subject to the player passing a medical.
"The Argentinian international will arrive at Manises-Valencia airport at 11.25pm local time and will undergo a medical tomorrow under the supervision of the Valencia Club de Futbol medical team."
Perez has appeared 11 times this league season for Benfica, scoring once - having scored four times in 28 appearances in each of his past two terms in Portugal.
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.