Madrid-born Juanfran already spent the 2014-15 campaign at Depor on loan from Watford, making 34 league starts to help the Galician side finish 16th in the Primera Division.
A statement from Deportivo read: “The club has reached an agreement with Watford and Juanfran for the player to join Deportivo on loan this coming season.
“Juanfran will arrive tonight in A Coruna and will join the team in training on Friday morning.”
After being on the books of Getafe, Villarreal and Real Madrid as a youngster, Juanfran made a name for himself at Real Betis.
The 26-year-old joined the Andalusian club on a free transfer two years ago and made 48 appearances in all competitions for Betis in the 2013-14 campaign.
Betis sold Juanfran’s sporting rights to Watford for a reported 1.5million euros last summer before the Hornets sent the player out on loan to Depor.
Juanfran is under contract with Watford until June 2016.