The 24-year-old had committed to an extended contract with Greek Superleague side Kalloni earlier this year.
His deal has since been terminated, however, and that has allowed the attacker to move to Tynecastle without the need for a fee to be paid.
Hearts have been tracking Delgado’s progress since the turn of the year with Kalloni, who finished 11th in Greece’s top flight last season.
He is the third player to move to the SPFL Championship winners this summer after Blazej Augustin and Gavin Reilly, the latter signing from Queen of the South on Tuesday.
Manager Robbie Neilson told Hearts News: “We spent a lot of time over the summer speaking to Juanma and meeting him. I’m delighted to get him.
“We thought it was going to get done a few weeks ago and we had some issues with the contractual situation in Greece but we finally got it over the line. I’m pleased to get it done.
“Craig (Levein, Hearts’ director of football) and Clive, Juanma’s agent, did a lot of work on it. He’ll be a big asset for us. He brings physicality and he’ll hopefully bring goals as well.
“He’s a good player, technically very good, great in the air, has good link-up play and he’s a great character so I’m pleased to get him.”