"Fernando Gago arrives this evening at the Hotel Valencia Palace after a pre-agreement was reached between Valencia, Real Madrid and the player himself," the La Liga side said on their official Twitter feed earlier in the week.
The 26-year-old Argentina international, who joined Real from Boca Juniors in 2007, is surplus to requirements at the Bernabeu and played last season on loan with AS Roma.
Spanish media reported Gago had agreed a four-year contract and would move for a fee of some five million euros.
Canales, meanwhile, was loaned out to the Mestalla last season, making 11 appearances and scoring once despite suffering a knee ligament injury in the spring.
The former Racing Santander midfielder is believed to make up eight million euros of the deal, with Gago comprising the other three-and-a-half.
Valencia finished third in La Liga last season and qualified for the Champions League group stages.